| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
J. Biol. Chem., Vol. 276, Issue 48, 44357-44364, November 30, 2001
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
From the Laboratory of Biochemistry, NHLBI, National Institutes
of Health, Bethesda, Maryland 20892-8012
In 1960, I went on sabbatical leave from the National
Institutes of Health (NIH) and spent the first 6 months in the
laboratory of Feodor Lynen in Munich and the second 6 months in the
laboratory of Georges Cohen at the Pasteur Institute in Paris. Both
were remarkable experiences. In Lynen's laboratory, I initiated a new project that led to the demonstration that vitamin
B12-coenzyme is required for the conversion of
methylmalonyl-CoA to succinyl-CoA (1-3). In Cohen's laboratory, I
participated in an ongoing project designed to elucidate the mechanism
involved in the regulation of aspartokinase activity in
Escherichia coli. This problem was of special interest
because it was well known that the ATP-dependent conversion
of aspartate to aspartyl phosphate is the first step in a branched
pathway that leads to the biosynthesis of three different amino acids,
lysine, threonine, and methionine. Working together with Cohen and his
co-worker, Gisele LeBras, we succeeded in separating two different
aspartokinases from E. coli extracts and obtained evidence
suggesting the existence of still another. One of these aspartokinases
was subject to specific feedback inhibition and to repression by
lysine, whereas the other was subject to feedback inhibition and to
repression by threonine (4, 5). This was the first demonstration that
multiple enzymes may be involved in the catalysis of initial steps in
branched metabolic pathways and that the levels and activities of each
one of the multiple enzymes may be differentially regulated by
repression and/or feedback inhibition by a particular product of one of
the branches in the pathway (6).
After returning to NIH, I resumed my studies on the metabolism
of heterocyclic compounds, a project that I had been working on before
going on sabbatical. This investigation was interrupted when a young
postdoctoral fellow, Clifford Woolfolk, joined the laboratory. He had
read the papers we had published on the regulation of aspartokinase and
was interested in working on that project in my laboratory. I informed
Clifford that all of that work had been carried out in Georges Cohen's
laboratory and that I did not feel it was appropriate to continue the
study at NIH. However, if he was interested in working on the
regulation of branched metabolic pathways, I would be pleased to
support the study of another enzyme that catalyzes the first common
step in a branched metabolic pathway. I suggested that he examine
metabolic maps and identify those enzymes that satisfied this criteria.
I emphasized also that the enzyme selected for study should be one for
which simple assays are available. Woolfolk came up with three
suggestions: glutamic dehydrogenase, glutamine synthetase
(GS),1 and
phosphoribosyl-pyrophosphate synthetase. His initial studies on
glutamic dehydrogenase revealed no feedback inhibitory characteristics. He then looked at E. coli GS and was rewarded by the finding
that the activity of this enzyme was subject to feedback inhibition by
seven different end products of glutamine metabolism, namely histidine,
tryptophan, AMP, CTP, carbamyl-P, glucosamine-6-P, and
NAD+, and also by glycine and alanine (7). This exciting
discovery initiated a dramatic change in the focus of much of the
research in the Laboratory of Biochemistry and for almost 35 years has occupied the time and energies of numerous highly talented postdoctoral fellows, visiting scientists, and senior associates, including Clifford
Woolfolk, B. M. Shapiro, Ann Ginsburg, P. Boon Chock, S. G. Rhee,
Wayne Anderson, Henry Kingdon, Amiel Segal, Michael Brown, Joseph
Ciardi, E. G. Engleman, Sharon Francis, J. S. Hubbard, J. J.
Villafranca, Stuart Adler, Richard Miller, K. Nakamura, Filiberto
Cimino, Stanley Prusiner, Thomas F. Deuel, S. B. Hennig, Steven
Tronick, D. Purich, S. Shaltiel, G. Magni, and Mark Fisher. In the
meantime, all of these participants have gone on to distinguish themselves as leading investigators in diverse fields of science.
In continuing studies, Woolfolk developed procedures for the
partial purification of GS from crude extracts of E. coli.
In studies with these enzyme preparations, he showed that whereas saturating levels of any one of the feedback inhibitors could only
partially inhibit activity of GS, mixtures of various combinations of
these inhibitors were more effective than any one alone and that a
combination of all of the inhibitors led to about 90% inhibition of GS
activity. It was clear from this study that the various inhibitors were
probably binding to different allosteric sites on the enzyme. This
finding together with results of kinetic measurements led to the
proposition that the activity of GS is regulated by a mechanism that we
refer to as cumulative feedback inhibition (7, 8). According
to this mechanism, overproduction of an end product of just one of the
metabolic branches could lead to inhibition of only that fraction of GS
that is needed to supply glutamine for the synthesis of that particular
end product. Additional feedback control of the first committed step in
the unique branch leading to that end product would presumably also be
subject to inhibition by the same end product, thus guaranteeing that
the uninhibited fraction of GS is then available only for synthesis of
end products of other branches in the metabolic pathway. Moreover, because their effects are more or less independent, overproduction of
the end product of another branch or branches in the pathway would have
a cumulative effect leading to further inhibition of the GS
activity as dictated by overall demand for its product, glutamine.
In 1966, Bennett Shapiro joined the Laboratory of
Biochemistry. He collaborated with Woolfolk in studies leading to the
isolation of GS as a homogeneous crystalline protein. Later in studies
with Ann Ginsburg, he established that GS is a large protein of about Mr 600,000, consisting of 12 apparently
identical Mr 50,000 subunits, and is dependent
on Mg(II) or Mn(II) for catalytic activity (9). Shapiro also showed
that upon treatment with EDTA the enzyme undergoes conversion to a
"relaxed" catalytically inactive configuration that is accompanied
by exposure of cysteine sulfhydryl groups (10), and upon treatment with
1 M urea this relaxed form of the enzyme undergoes
time-dependent complete subunit dissociation. Moreover,
upon addition of Mn(II) or Mg(II) the subunits can undergo re-association to a "tightened" configuration with activities comparable with that of the native, so-called "taut," form (11). Subsequently, Mark Fisher demonstrated that in the presence of ATP the
dissociated subunits could also be converted to the "taut" form by
the E. coli chaperonin (12). In continuing studies, Shapiro
and Ginsburg demonstrated that GS has two binding sites for divalent
cations; one is involved in the interconversion of the "relaxed"
and "tightened" configurations, whereas the other is involved in
the binding of the ATP substrate to the enzyme (13, 14). Subsequently,
Shapiro took a sample of the pure enzyme to the National Institute for
Medical Research in London, where R. C. Valentine, an expert in
electron microscopy, examined its structure. They confirmed that the
enzyme is composed of 12 subunits and showed that the subunits were
arranged in two superimposed hexagonal arrays. They showed further that
the "relaxed" form of the enzyme obtained by EDTA treatment
retained the dodecameric structure, but upon conversion to the
"taut" form by the addition of Mn(II) the double hexagon molecules
underwent face-to-face interactions forming long hexagonal tubes that
subsequently undergo lateral associations to form paracrystalline
"wheat-shaped" structures (15). Needless to say, GS became the
subject of numerous detailed kinetic studies by Boon Chock, Ann
Ginsburg, S. G. Rhee, and their co-workers, but it is beyond the scope
of this presentation to summarize the results of those studies.
When the original supply of pure GS obtained by Shapiro and
Woolfolk was nearly exhausted, it became necessary to prepare a new
batch of the enzyme. About this time, Henry Kingdon joined the
laboratory as a clinical associate. His first assignment was to isolate
a new sample of GS from crude extracts of E. coli using the
procedure developed by Woolfolk and Shapiro. Much to our surprise and
considerable concern, the new homogeneous enzyme preparation was
insensitive to inhibition by most of the end products that had been
shown to inhibit the earlier batch of enzyme. In addition, the new GS
preparation was almost completely dependent on the presence of Mg(II)
for catalytic activity, whereas the earlier preparation exhibited
greater activity with Mn(II). The amino acid compositions of both
preparations were identical, indicating that we were dealing with the
same protein. Other studies established that the difference in
activities was not because of the isolation procedure, differences in
assay conditions, changes during storage, or interconversion between
taut and relaxed forms. However, there was a difference in the E. coli growth conditions used for the preparation of cell-free
extracts. The first GS preparation was isolated from cells grown in
media containing glycerol and glutamate as the sole carbon and nitrogen
sources, and the cells were harvested in the stationary phase of
growth, whereas the second batch of GS was from cells grown on media
containing glucose and growth-limiting levels of ammonium chloride and
was harvested during the log phase of growth. In subsequent studies, it
was confirmed that these differences in growth conditions were
responsible for the observed differences in enzyme characteristics
(16). However, it did not explain why the two apparently identical
enzyme preparations differed in their sensitivities to feedback
inhibition and divalent cation specificity. This was finally resolved
when a comparison of the UV spectra revealed that the first preparation
exhibited a higher absorbance at 260 nm, suggesting the presence of a
nucleotide adduct (17). This was confirmed by showing that treatment of the older preparation with snake venom phosphodiesterase led to the
release of AMP and conversion of the enzyme to a form that was
insensitive to feedback inhibition (17). It soon became evident that
the susceptibility of GS to cumulative feedback inhibition is under
strict control by a novel mechanism involving the adenylylation of a
specific amino acid residue in each subunit of the enzyme. These
results led also to the consideration that if adenylylation represents
an important mechanism for the regulation of GS activity, then there
should be enzymes that catalyze the interconversion of GS between
adenylylated and unadenylylated forms, in analogy to the kinase- and
phosphatase-catalyzed interconversion of some enzymes between
phosphorylated and unphosphorylated forms. Led by this consideration,
Kingdon et al. (18) identified a highly specific
adenylyltransferase (ATase) in E. coli extracts that catalyzes transfer of the AMP moiety of ATP to the hydroxyl group of a
particular tyrosyl residue in each subunit of GS with concomitant formation of inorganic pyrophosphate. In further studies, it was established that, depending on the time of incubation and the concentration of transferase used, preparations of GS containing 1-12
adenylylated subunits could be obtained and that the fraction of a
given GS preparation that could be inhibited by various feedback inhibitors was governed by the number of adenylylated subunits that it contained.
Shapiro also demonstrated that cell-free extracts contained an activity
that could catalyze the removal of adenylyl groups on GS (19).
Curiously, he found that two separable protein fractions (PI and PII) were required for maximal
deadenylylation activity. This activity was dependent upon the presence
of Mn(II), At this stage of development of the problem, Amiel Segal and
Michael Brown joined the Laboratory of Biochemistry and were charged
with the responsibility of trying to elucidate further the interaction
between ATase and the PII protein and also to elucidate the
puzzling role of UTP in this process. They found that, like GS, the
PII protein exists in two forms: (a) an
unmodified form that in the presence of glutamine stimulates the
adenylylation of GS by interactions at the adenylylation site (ATa) of
the ATase and (b) a uridylylated form (PII-UMP)
that in the absence of glutamine and in the presence of
2-oxoglutarate stimulates the deadenylylation of GS by interactions
at the deadenylylation site (ATd) of ATase (25). This led to further
studies by Mangum et al. on the role of
PII in GS regulation (26) and studies by Garcia and Rhee (27) showing that the uridylylation and deuridylylation of
PII is catalyzed by the same uridylyltransferase (UTase).
Subsequently, Adler et al. (28) obtained a homogeneous
preparation of PII and showed that it is a protein of about
Mr 44,000, which was later shown by other
workers to be a trimer (29). In continuing studies, Adler and Purich
showed that uridylylation of PII involves covalent
attachment of a uridylyl group from UTP to a particular tyrosine
residue in each subunit (Reaction 3, where n = 1-3)
and that deuridylylation of the uridylylated PII is a
hydrolytic process (Reaction 4).
In view of the results summarized above, it became evident
that the activity of GS in E. coli is finely controlled by a
cascade system composed of two tightly linked interconvertible
enzyme/protein cycles, each one of which is catalyzed by a bifunctional
enzyme (Fig. 1). From a detailed analysis
of the enzymes involved in this bicyclic cascade, it was found that the
activity of GS is subject to regulation by over 40 metabolites. Some of
these exert their effects by interacting directly with GS, whereas
others serve as substrates or allosteric effectors of one or both of the enzymes, ATase and UTase, that catalyze the nucleotidylation and
denucleotidylation reactions of GS and the PII protein. Of these effectors, 2-oxoglutarate, glutamate, ATP, UTP, and
Pi are of special significance. The latter three compounds
serve as co-substrates in the nucleotidylation/denucleotidylation
reactions, whereas glutamine and 2-oxoglutarate serve as important
allosteric effectors of the bifunctional enzymes. Glutamine inhibits
and 2-oxoglutarate stimulates the ability of ATase to catalyze the
PII-dependent adenylylation of GS, whereas each
effector has an opposite effect on the capacity of ATase to catalyze
the deadenylylation of GS. In an analogous manner, glutamine inhibits
the ability of UTase to catalyze the uridylylation of PII
and to stimulate its ability to catalyze the deuridylylation of
PII-UMP. In contrast, 2-oxoglutarate stimulates the
uridylylation of PII. The diverse effects of these various
effectors on the activity of GS led to the proposition that the dynamic
interconversion of an enzyme between covalently modified and unmodified
forms provides a mechanism by which the activity of an enzyme can be
shifted gradually from one level to another commensurate with cellular
demand. This concept was supported by the studies of Brown et
al. (25) showing that the fraction of GS subunits that could be
adenylylated varied in response to changes in the levels of multiple
metabolites that govern the activities of the cascade enzymes. Thus,
when GS was incubated in a mixture containing ATP, UTP, Pi,
2-oxoglutarate, glutamine, Mg(II), and/or Mn(II) and the two
bifunctional enzymes, ATase and UTase, within a few minutes the average
number of adenylylated subunits in GS reached a steady-state value.
Moreover, a change in the concentration of any one of the five
metabolites or Mn(II) produced a shift in the level of adenylylated
subunits, either to higher or lower values depending upon which
metabolite concentration was varied. It was further observed that after
a steady-state level of adenylylation was established, the
concentration of ATP continued to decrease, indicating that under a
specified set of conditions a dynamic steady state is established in
which the rates of adenylylation and deadenylylation of GS are equal.
It follows that the steady-state level of adenylylated subunits and, therefore, the specific catalytic activity of GS and its susceptibility to cumulative feedback inhibition are specified by the relative concentrations of the positive and negative effectors (metabolites) that govern activities of the cascade enzymes. In subsequent studies, Rhee and co-workers (30-33) took advantage of molecular biological techniques to obtain strains of E. coli that overproduce
UTase and PII and were able to obtain highly purified
preparations of these proteins. Then, in a monumental effort, they
determined the values of 21 interaction constants that govern the
protein/protein and protein/effector interactions that are involved in
various steps of the GS bicyclic cascade. With this knowledge, it was possible to carry out in vitro experiments that verified in
every important detail the theoretical predictions of the cascade
model. Furthermore, verification of these basic principles was obtained by Umberto Mura in studies on the adenylylation of GS in permeabilized E. coli cells, subjected to varying concentrations of ATP,
UTP, 2-oxoglutarate, glutamine, and Pi (34, 35).
A University of Maryland graduate student, Robert Hohman, was
granted permission to carry out his thesis research in the Laboratory of Biochemistry. His studies were concerned with the development of
AMP-specific antibodies that could be used to separate adenylylated and
unadenylylated forms of GS and that could detect variations in protein
configurations elicited by partial adenylylation of the enzyme or by
allosteric interactions. From a comparison of the extent of
immunoprecipitation of GS preparations containing various ratios of
adenylylated/unadenylylated subunits, it was established that the
initial binding of antibodies to GS is a function of the total number
of adenylylated subunits per dodecamer and that partially adenylylated
enzyme preparations are composed of subpopulations of GS molecules that
differ in their tendency to form precipitable aggregates due presumably
to differences in the topographical distribution of antigenic
determinants on the surface of the enzyme. Some distributions may favor
intramolecular reactions of the bivalent antibody with two different
adenylylated subunits within the same GS molecule to form soluble
immune complexes, whereas other distributions may favor intermolecular
cross-linkage of the bivalent antibodies with adenylyl groups of two
different molecules leading to precipitation. Significantly, results of these studies highlight the fact that immunoprecipitibility of multivalent protein antigens by bivalent antibodies is a function of
the intramolecular epitope density (36-38).
Based on the results summarized above, my colleague, Boon
Chock, an expert enzyme kineticist, carried out a detailed theoretical analysis of a bicyclic cascade system analogous to that described above
for the regulation of GS activity (39-43). This analysis revealed that
coupled cyclic cascade systems are endowed with regulatory potentials
far beyond our imagination. It was shown that: (a) cascades
are capable of signal amplification, i.e. the concentration
of an effector needed to provoke a large change in the level of the
covalently modified target enzyme can be orders of magnitude lower than
the Km for the binding of that effector to converter
enzymes; (b) cascades can serve as rate amplifiers and,
therefore, can facilitate a change from one steady-state level of
covalent modification to another within the millisecond time range;
(c) cascades are capable of generating high cooperativity (sigmoidal response) to increasing concentrations of a given effector; (d) cascades serve as metabolic integration systems. They
are able to monitor continuously the intracellular concentrations of a
large number of metabolites. This leads to continuous shifts in the
steady-state ratio of covalently modified and unmodified forms of an
enzyme and, therefore, to changes in its activity commensurate with
metabolic demand. With these properties, it is understandable that
mechanisms involving reversible covalent modifications of proteins are
widely used in cellular regulation of signal transduction.
Thus ended a most enlightening and rewarding story of GS regulation.
However, it was the beginning of another story in which GS has played a
dominant role. As an outgrowth of our studies in the field of
regulation, I became aware of the fact that the intracellular
concentrations of many enzymes are determined by the nutritional state
of the organism. In response to nitrogen or carbon starvation, the
concentration of a given enzyme may either increase or decrease.
Although considerable information was available on the mechanism of
protein synthesis, almost nothing was known about the mechanism(s)
involved in the regulation of protein degradation. In studies designed
to learn more about the latter, it was demonstrated that when either
E. coli or Aerobacter aerogenes is forced into a
state of stationary growth by nitrogen limitation, there is a rapid
decline in the level of GS and several other enzymes. It was then
established that under these conditions, the proteolytic degradation of
GS is initiated by reactive oxygen-mediated oxidative inactivation of
the enzyme. This was the beginning of another chapter in the GS story
that has led to the elucidation of biochemical mechanisms involved in
the oxidative inactivation of proteins and the role they play in
protein degradation, aging, and in a number of diseases. It is beyond
the scope of this article to summarize these studies (for review, see
Refs. 44 and 45).
The story of GS reviewed here summarizes results of studies carried out
in the Laboratory of Biochemistry, NHLBI, National Institutes of
Health. I have not referred to studies carried out in H. Holzer's
laboratory in Freiburg, Germany, that were carried out in parallel to
those described here and led to similar findings (46-49) (for reviews
by Holzer et al., see also Refs. 19, 25, 26, 50, and 51 for
discussions of the relationships between our results and those in
Holzer's laboratory). Also, I have not described the results of
beautiful experiments by David Eisenberg on the crystal structure of GS
(52-54), extending our knowledge of its structure and confirming in
many respects the conclusions arrived at from our studies.
Published, JBC Papers in Press, October 3, 2001, DOI 10.1074/jbc.R100055200
The abbreviations used are:
GS, glutamine
synthetase;
ATase, adenylyltransferase;
UTase, uridylyltransferase.
REFLECTIONS
The Story of Glutamine Synthetase Regulation
INTRODUCTION
From Aspartokinase to Glutamine Synthetase
Cumulative Feedback Regulation
GS Structure and Physical Characteristics
Adenylylation of GS Governs Its Susceptibility to Feedback
Inhibition
-ketoglutarate, UTP, and inorganic phosphate and was also
greatly stimulated by the presence of ATP (20). The requirement for
inorganic phosphate was explained later when Wayne Anderson showed that
the deadenylylation reaction involves a phosphorolytic cleavage of the
adenylyl-O-tyrosyl bond, yielding ADP and unadenylylated GS
(21). In further experiments, Anderson, together with Barbara Hennig
and Ann Ginsburg, purified Shapiro's PI protein and showed
that it was, in fact, an ATase that could catalyze both the
adenylylation and deadenylylation of GS (Reactions 1 and 2 in which
n = 1-12) and that its activity was modulated by the
PII protein and by glutamine, 2-oxoglutarate, ATP, and
UTP (22-24).
Purification of the PII Regulatory Protein and the
Demonstration That Its Regulatory Activity Is Subject to
Uridylylation and Deuridylylation of a Tyrosine Residue
The Bicyclic Cascade
View larger version (17K):
[in a new window]
Fig. 1.
The bicyclic cascade that regulates GS
activity. Interrelationship between the cyclic interconversion of
the regulatory protein between uridylylated
(PII(UMP)4) and unuridylylated
(PII) forms, and the cyclic interconversion of GS between
adenylylated (GS(AMP)12) and unadenylylated forms, and the
reciprocal control of these interconversions by L-glutamine
(Gln) and -ketoglutarate (-KG). ATa and
ATd denote the adenylylation and deadenylylation sites of
adenylyltransferase, respectively; UTd and UTu
denote the deuridylylation and uridylylation sites of
uridylyltransferase, respectively. Reprinted with permission
from Rhee et al. (Rhee, S. G., Chock, P. B., and Stadtman,
E. R. (1985) in The Enzymology of
Post-translational Modification of
Proteins (Freedman, P. B., and Hawkins, H. C., eds) Vol.
2, pp. 273-297, Academic Press, New York).
Immunochemical Studies
Theoretical Analysis of Cyclic Cascades
FOOTNOTES
ABBREVIATIONS
REFERENCES
1.
Stadtman, E. R.,
Overath, P.,
Eggerer, H.,
and Lynen, F.
(1959)
The role of biotin and vitamin B12 in propionate metabolism. Biochem.
Biophys. Res. Commun.
2,
1-7
2.
Eggerer, H.,
Overath, P.,
Lynen, F.,
and Stadtman, E. R.
(1960)
On the mechanism of the cobamide coenzyme-dependent isomerization of methylmalonyl-CoA to succinyl-CoA.
J. Am. Chem. Soc.
82,
2643
3.
Stadtman, E. R.,
Overath, P.,
Eggerer, H.,
and Lynen, F.
(1961)
The function of biotin and vitamin B12-coenzyme in the oxidation of fatty acids with an uneven number of carbon atoms. In Proceedings of the Symposium on Drugs Affecting Lipid Metabolism
, pp. 68-74, Elsevier Science Publishers B.V., Amsterdam
4.
Stadtman, E. R.,
Cohen, G. N.,
LeBras, G.,
and deRobichon-Szulmajster, H.
(1961)
Feedback inhibition and repression of aspartokinase activity in Escherichia coli and Saccharomyces cerevisiae.
J. Biol. Chem.
236,
2033-2038
5.
Stadtman, E. R.,
Cohen, G. N.,
and LeBras, G.
(1961)
Feedback inhibition and repression of aspartokinase activity in Escherichia coli.
Ann. N. Y. Acad. Sci.
94,
952-959
6.
Stadtman, E. R.
(1963)
Symposium of multiple forms of enzymes and control mechanisms. II. Enzyme multiplicity and function in the regulation of divergent metabolic pathways.
Bacteriol. Rev.
27,
170-181
7.
Woolfolk, C. A.,
and Stadtman, E. R.
(1964)
Cumulative feedback inhibition in the multiple end-product regulation of glutamine synthetase activity in Escherichia coli.
Biochem. Biophys. Res. Commun.
17,
313-319
8.
Woolfolk, C. A.,
and Stadtman, E. R.
(1967)
Regulation of glutamine synthetase. III. Cumulative feedback inhibition of glutamine synthetase from Escherichia coli.
Arch. Biochem. Biophys.
118,
736-755
9.
Woolfolk, C. A.,
Shapiro, B.,
and Stadtman, E. R.
(1966)
Regulation of glutamine synthetase. I. Purification and properties of glutamine synthetase from Escherichia coli.
Arch. Biochem. Biophys.
116,
177-192
10.
Shapiro, B. M.,
and Stadtman, E. R.
(1967)
Regulation of glutamine synthetase. IX. Reactivity of the sulfhydryl groups of the enzyme from Escherichia coli.
J. Biol. Chem.
242,
5069-5079
11.
Woolfolk, C. A.,
and Stadtman, E. R.
(1967)
Regulation of glutamine synthetase. IV. Reversible dissociation and inactivation of glutamine synthetase from Escherichia coli by the concerted action of EDTA and urea.
Arch. Biochem. Biophys.
122,
174-189
12.
Fisher, M. T.
(1992)
Promotion of the in vitro regeneration of dodecameric glutamine synthetase from Escherichia coli in the presence of GroEL (chaperonin-60) and ATP.
Biochemistry
31,
3955-3963
13.
Shapiro, B. M.,
and Ginsburg, A.
(1968)
Effects of specific divalent cations on some physical and chemical properties of glutamine synthetase from Escherichia coli. Taut and relaxed enzyme forms.
Biochemistry
7,
2153-2167
14.
Denton, M. D.,
and Ginsburg, A.
(1969)
Conformational changes in glutamine synthetase from Escherichia coli. I. The binding of Mn2+ in relation to some aspects of the enzyme structure and activity.
Biochemistry
8,
1714-1725
15.
Valentine, R. C.,
Shapiro, B. M.,
and Stadtman, E. R.
(1968)
Regulation of glutamine synthetase. XII. Electron microscopy of the enzyme from Escherichia coli.
Biochemistry
7,
2143-2152
16.
Kingdon, H. S.,
and Stadtman, E. R.
(1967)
Regulation of glutamine synthetase. X. Effect of growth conditions on the susceptibility of Escherichia coli glutamine synthetase to feedback inhibition.
J. Bacteriol.
94,
949-957
17.
Shapiro, B. M.,
Kingdon, H. S.,
and Stadtman, E. R.
(1967)
Regulation of glutamine synthetase. VII. A new form of the enzyme with altered regulatory and kinetic properties.
Proc. Natl. Acad. Sci. U. S. A.
58,
642-649
18.
Kingdon, H. S.,
Shapiro, B. M.,
and Stadtman, E. R.
(1967)
Regulation of glutamine synthetase. VIII. ATP:glutamine synthetase adenylyltransferase. An enzyme that catalyzes alteration in the regulatory properties of glutamine synthetase.
Proc. Natl. Acad. Sci. U. S. A.
58,
1703-1710
19.
Shapiro, B. M.,
and Stadtman, E. R.
(1968)
Glutamine synthetase deadenylylating enzyme.
Biochem. Biophys. Res. Commun.
30,
32-37
20.
Shapiro, B. M.
(1969)
The glutamine synthetase deadenylylation enzyme from Escherichia resolution into two components, specific nucleotide stimulation and cofactor requirements.
Biochemistry
8,
659-710
21.
Anderson, W. B.,
and Stadtman, E. R.
(1970)
Glutamine synthetase deadenylylation reaction yielding ADP as nucleotide product.
Biochem. Biochem. Res. Commun.
41,
704-709
22.
Anderson, W. B.,
Hennig, S. B.,
Ginsburg, A.,
and Stadtman, E. R.
(1970)
Association of ATP:glutamine synthetase adenylyltransferase activity with PI component of the glutamine synthetase adenylylation system.
Proc. Natl. Acad. Sci. U. S. A.
67,
1417-1424
23.
Hennig, S. B.,
Anderson, W. B.,
and Ginsburg, A.
(1970)
Adenosine triphosphate:glutamine synthetase adenylyltransferase of Escherichia coli glutamine synthetase: two active forms.
Proc. Natl. Acad. Sci. U. S. A.
67,
1761-1768
24.
Anderson, W. B.,
and Stadtman, E. R.
(1971)
Purification and functional roles of the PI and PII components of Escherichia coli glutamine synthetase deadenylylation system.
Arch. Biochem. Biophys.
143,
428-443
25.
Brown, M. S.,
Segal, A.,
and Stadtman, E. R.
(1971)
Modulation of glutamine synthetase adenylylation and deadenylylation is mediated by nucleotide transformation of the PII regulatory protein (E. coli/protein-bound uridine nucleotide/adenylyltransferase/2-oxo-glutarate-cascade regulation).
Proc. Natl. Acad. Sci. U. S. A.
68,
2949-2953
26.
Mangum, J. H.,
Magni, G.,
and Stadtman, E. R.
(1973)
Regulation of glutamine synthetase deadenylylation by the enzymatic uridylylation and deuridylylation of the PII regulatory protein.
Arch. Biochem. Biophys.
158,
514-525
27.
Garcia, E.,
and Rhee, S. G.
(1983)
Cascade control of Escherichia coli glutamine synthetase. Purification and properties of PII uridylyltransferase and uridylyl-removing enzyme.
J. Biol. Chem.
258,
2246-2253
28.
Adler, S. P.,
Purich, D.,
and Stadtman, E. R.
(1975)
Cascade control of Escherichia coli glutamine synthetase. Properties of the PII regulatory protein and the uridylyltransferase-uridylyl removing enzyme.
J. Biol. Chem.
16,
6264-6272
29.
Carr, P. D.,
Cheah, E.,
Suffolk, P. M.,
Vasudevan, S. G.,
Dixon, N. E.,
and Ollis, D. L.
(1996)
X-ray structure of the signal transduction protein P-II from Escherichia coli at 1.9 angstrom.
Acta Crystallogr.
52,
93-104
30.
Rhee, S. G.,
Park, S. C.,
and Koo, J. H.
(1985)
The role of adenylyltransferase and uridylyltransferase in the regulation of glutamine synthetase in Escherichia coli.
Curr. Top. Cell Regul.
27,
221-231
31.
Rhee, S. G.,
and Chock, P. B.
(1983)
Purification and characterization of uridylylated and unuridylylated forms of regulatory protein PII involved in the glutamine synthetase regulation in Escherichia coli. Isoenzymes
Curr. Top. Biol. Med. Res.
8,
141-153
32.
Son, H. S.,
and Rhee, S. G.
(1987)
Cascade control of Escherichia coli glutamine synthetase.
J. Biol. Chem.
262,
8690-8695
33.
Suh, S. W.,
and Rhee, S. G.
(1983)
Preliminary x-ray crystallographic studies and molecular symmetry of the PII regulatory protein from Escherichia coli.
J. Biol. Chem.
258,
10294-10295
34.
Mura, U.,
and Stadtman, E. R.
(1981)
Glutamine synthetase adenylylation in permeabilized cells of Escherichia coli.
J. Biol. Chem.
256,
13014-13021
35.
Mura, U.,
Chock, P. B.,
and Stadtman, E. R.
(1981)
Allosteric regulation of the state of adenylylation of glutamine synthetase in permeabilized cell preparations of Escherichia coli.
J. Biol. Chem.
256,
13022-13029
36.
Hohman, R. J.,
and Stadtman, E. R.
(1978)
Use of AMP-specific antibodies to differentiate between adenylylated and unadenylylated E. coli glutamine synthetase.
Biochem. Biophys. Res. Commun.
82,
865-870
37.
Hohman, R. J.,
Rhee, S. G.,
and Stadtman, E. R.
(1980)
Anti-AMP antibody precipitation of multiply adenylylated forms of glutamine synthetase from E. coli.
Proc. Natl. Acad. Sci. U. S. A.
77,
7410-7414
38.
Hohman, R. J.,
and Stadtman, E. R.
(1982)
Relationship between epitope density and immunoprecipitation of multivalent antigens by bivalent antibody: immunoprecipitation of adenylylated glutamine synthetase by anti-AMP antibodies.
Arch. Biochem. Biophys.
218,
548-560
39.
Stadtman, E. R.,
Chock, P. B.,
and Adler, S. P.
(1975)
in
Metabolic regulation of coupled covalent modification cascade systems. In Metabolic Interconversion of Enzymes
(Shaltiel, S., ed)
, pp. 142-149, Springer-Verlag New York Inc., New York
40.
Stadtman, E. R.,
and Chock, P. B.
(1977)
Superiority of interconvertible enzyme cascades in metabolic regulation: analysis of monocyclic systems.
Proc. Natl. Acad. Sci. U. S. A.
74,
2761-2765
41.
Chock, P. B.,
and Stadtman, E. R.
(1977)
Superiority of interconvertible enzyme cascades in metabolic regulation: analysis of multicyclic systems.
Proc. Natl. Acad. Sci. U. S. A.
74,
2766-2770
42.
Shacter, E.,
Chock, P. B.,
and Stadtman, E. R.
(1984)
Regulation through phosphorylation/dephosphorylation cascade systems.
J. Biol. Chem.
259,
12252-12259
43.
Shacter, E.,
Chock, P. B.,
and Stadtman, E. R.
(1984)
Energy consumption in a cyclic phosphorylation/dephosphorylation cascade.
J. Biol. Chem.
259,
12260-12264
44.
Berlett, B. S.,
and Stadtman, E. R.
(1997)
Protein oxidation in aging, disease, and oxidative stress.
J. Biol. Chem.
272,
20313-20316
45.
Stadtman, E. R.,
and Berlett, B. S.
(1998)
Reactive oxygen-mediated protein oxidation in aging and disease.
Drug Metab. Rev.
30,
225-243
46.
Holzer, H.,
Mecke, D.,
Liess, K.,
Wulff, K.,
Heilmeyer, E., Jr.,
Gancedo, C.,
Schutt, H.,
Battig, A.,
Heinrich, P.,
and Wolf, D.
(1969)
Enzyme-catalyzed chemical modification of glutamine synthetase from E. coli.
FEBS Symp.
19,
171-177
47.
Holzer, H.
(1969)
in
Characterization of glutamine synthetase inactivating and activating enzyme from Escherichia coli. In Alfred Benson Symposium I. The Role of Nucleoside for the Function and Conformation of Enzymes
(Kalckar, H. M.
, Klenow, H.
, Ottesen, M.
, Munch-Petersen, A.
, and Thaysen, J. H., eds)
, pp. 94-110, Munksgaard Press, Copenhagen, Denmark
48.
Holzer, H.
(1969)
Regulation of enzymes by enzyme-catalyzed chemical modification.
Adv. Enzymol.
32,
297-326
49.
Ebner, E.,
Wolf, D.,
Gancedo, C.,
Elsasser, S.,
and Holzer, H.
(1970)
ATP:glutamine synthetase adenylyltransferase from Escherichia coli B. Purification and properties.
Eur. J. Biochem.
14,
535-544
50.
Stadtman, E. R.
(1969)
in
On the structure and allosteric regulation of glutamine synthetase from Escherichia coli. In Alfred Benson Symposium I. The Role of Nucleoside for the Function and Conformation of Enzymes
(Kalckar, H. M.
, Klenow, H.
, Ottesen, M.
, Munch-Petersen, A.
, and Thaysen, J. H., eds)
, pp. 142-149, Munksgaard Press, Copenhagen, Denmark
51.
Shapiro, B. M.,
and Stadtman, E. R.
(1970)
The regulation of glutamine synthetase in microorganisms.
Annu. Rev. Microbiol.
24,
501-524
52.
Almassy, R. J.,
Janson, C. A.,
Hamlin, R.,
Xuong, N. H.,
and Eisenberg, D.
(1986)
Novel subunit-subunit interactions in the structure of glutamine synthetase.
Nature
323,
304-309
53.
Yamashita, M. N.,
Almassy, R. J.,
Janson, C. A.,
Casicio, D.,
and Eisenberg, D.
(1989)
Refined atomic model of glutamine synthetase at 3.5 Å resolution.
J. Biol. Chem.
264,
17681-17690
54.
Liaw, S.-H.,
Pan, C.,
and Eisenberg, D.
(1993)
Feedback inhibition of fully unadenylylated glutamine synthetase from Salmonella typhimurium by glycine, alanine, and serine.
Proc. Natl. Acad. Sci. U. S. A.
90,
4996-5000
Copyright © 2001 by The American Society for Biochemistry and Molecular Biology, Inc.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
This article has been cited by other articles:
|
|
 |
|
  S. Kurihara, S. Oda, Y. Tsuboi, H. G. Kim, M. Oshida, H. Kumagai, and H. Suzuki {gamma}-Glutamylputrescine Synthetase in the Putrescine Utilization Pathway of Escherichia coli K-12 J. Biol. Chem., July 18, 2008; 283(29): 19981 - 19990. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Carroll, C. A. Pashley, and T. Parish Functional Analysis of GlnE, an Essential Adenylyl Transferase in Mycobacterium tuberculosis J. Bacteriol., July 15, 2008; 190(14): 4894 - 4902. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 L. Lima, A. Seabra, P. Melo, J. Cullimore, and H. Carvalho Post-translational regulation of cytosolic glutamine synthetase of Medicago truncatula J. Exp. Bot., August 1, 2006; 57(11): 2751 - 2761. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Y. Zhang, D. M. Wolfe, E. L. Pohlmann, M. C. Conrad, and G. P. Roberts Effect of AmtB homologues on the post-translational regulation of nitrogenase activity in response to ammonium and energy signals in Rhodospirillum rubrum Microbiology, July 1, 2006; 152(7): 2075 - 2089. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Y. Zhu, M. C. Conrad, Y. Zhang, and G. P. Roberts Identification of Rhodospirillum rubrum GlnB Variants That Are Altered in Their Ability To Interact with Different Targets in Response to Nitrogen Status Signals. J. Bacteriol., March 1, 2006; 188(5): 1866 - 1874. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Kresge, R. D. Simoni, and R. L. Hill Fatty Acid Synthesis and Glutamine Synthetase: the Work of Earl Stadtman J. Biol. Chem., July 1, 2005; 280(26): e23 - e23. [Full Text] [PDF]
|
|
|
|
|
|
Y. Zhang, E. L. Pohlmann, and G. P. Roberts GlnD Is Essential for NifA Activation, NtrB/NtrC-Regulated Gene Expression, and Posttranslational Regulation of Nitrogenase Activity in the Photosynthetic, Nitrogen-Fixing Bacterium Rhodospirillum rubrum J. Bacteriol., February 15, 2005; 187(4): 1254 - 1265. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. B.G. Moorhead and C. S. Smith Interpreting the Plastid Carbon, Nitrogen, and Energy Status. A Role for PII? Plant Physiology, October 1, 2003; 133(2): 492 - 498. [Full Text] [PDF]
|
|
|
|
|
|
V. K. Mutalik, P. Shah, and K. V. Venkatesh Allosteric Interactions and Bifunctionality Make the Response of Glutamine Synthetase Cascade System of Escherichia coli Robust and Ultrasensitive J. Biol. Chem., July 11, 2003; 278(29): 26327 - 26332. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
TOP
INTRODUCTION
From Aspartokinase to Glutamine...