| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
(Received for publication, June 15, 1995) From the
Adenylate cyclase toxin from Bordetella pertussis requires posttranslational acylation of lysine 983 for the ability
to deliver its catalytic domain to the target cell interior and produce
cyclic adenosine monophosphate (cell-invasive activity) and to form
transmembrane channels (hemolytic activity). When the toxin is
expressed in Escherichia coli, it has reduced hemolytic
activity, but comparable cell-invasive activity to that of adenylate
cyclase toxin from B. pertussis. In contrast to the native
protein from B. pertussis, which is exclusively palmitoylated,
recombinant toxin from E. coli is acylated at lysine 983 with
about 87% palmitoylated and the remainder myristoylated. Furthermore,
the recombinant toxin contains an additional palmitoylation on
approximately two-thirds of the lysines at position 860. These
observations suggest that the site and nature of posttranslational
fatty-acylation can be dictated by the bacterial host used for
expression and can have a significant, but selective, effect on protein
function.
Adenylate cyclase (AC) ( The AC toxin gene (cyaA) has been cloned and sequenced by
Glaser et al.(10, 11) and the AC toxin locus
was noted to have homologies with the Escherichia coli hemolysin operon and that of other RTX toxins. These toxins are
characterized by a set of glycine- and aspartate-rich nonapeptide
repeats(12, 13) . The formation of biologically active
AC toxin requires an accessory protein expressed from an upstream gene, cyaC(14) . That protein, CyaC, appears to be involved
in posttranslational activation of AC toxin. Recently, tandem mass
spectrometry was used to determine that the modification on native AC
toxin from Bordetella pertussis (Bp-CyaA) consists of
palmitoylation on the It has been observed
previously that recombinant AC toxin expressed in E. coli exhibits cell-invasive activity identical to the native toxin, but
hemolytic activity which is severalfold reduced(17) . In order
to determine whether the nature of the acylation could be the basis of
this functional difference, wild type AC toxin from B. pertussis and recombinant AC toxin from E. coli were analyzed by
mass spectrometry. We report here that despite the presence of the same
requisite CyaC, the pattern and chemical nature of the acylation are
different when AC toxin (CyaA) is expressed in these two organisms.
The fermentor cultures of E. coli strains were supplied by the Service of Fermentations
of Institut Pasteur (Paris). The r-CyaA and r-proCyaA were extracted
from E. coli cell debris after French press disruption, as
described previously(17) . Bp-CyaA was extracted from washed B. pertussis cells with 4 M urea as described
previously(5) . The different CyaAs were purified close to
homogeneity by a combination of ion-exchange chromatography (19) and affinity chromatography(17) . In the final
step CyaAs were eluted from calmodulin-agarose columns with 8 M urea, 50 mM Tris-HCl, pH 8.0, 2 mM EDTA, and
frozen at -70 °C.
CyaC-activated recombinant AC toxin (r-CyaA) was produced in E. coli(17, 18) and compared with Bp-CyaA
extracted from the natural producer B. pertussis. It was found
that the partially purified r-CyaA had about 4-fold lower specific
hemolytic activity on sheep erythrocytes and 4-10-fold lower
specific pore-forming activity in artificial planar lipid bilayers than
Bp-CyaA (9) , whereas the cell-invasive activity of both
proteins was equal. In the present studies, r-CyaA and Bp-CyaA were
mixed at different molar ratios, so as to yield a fixed total CyaA
concentration of 1 unit/ml, and the cell-invasive and hemolytic
activities of the mixtures were determined. The cell-invasive AC
activity was constant regardless of the molar ratio of the proteins in
the mixture (Fig. 1). In contrast, the hemolytic activity of the
mixture increased with the increasing proportion of the Bp-CyaA present
in the mixture, yielding an upwardly concave curve. Because both
cell-invasive and hemolytic activities depend on the posttranslational
fatty-acylation of Lys
Figure 1:
Comparison of cell-invasive and
hemolytic activities of r-CyaA and Bp-CyaA. Toxin dilutions and/or
mixtures were prepared in 50 mM Tris-HCl, pH 8.0, 8 M urea, and 2 mM EDTA. R-CyaA and Bp-CyaA were mixed at
various molar ratios to obtain the final solutions at 100 units/ml (200
µg/ml) of total CyaA, and the toxin mixtures were directly diluted
to 1 unit/ml (100-fold) into prewarmed suspensions of washed sheep
erythrocytes (5
When characterized by mass spectrometry, both native
Bp-CyaA and r-CyaA matched the amino acid sequence deduced from the
published nucleotide sequence of the cyaA gene (10, 17) and exhibited the following posttranslational
modifications. Bp-CyaA has previously been shown to bear a single
modification consisting of a palmitoylation at the
Figure 2:
Most
of Lys
Both Lys
Figure 3:
Lys
Because of its conservation in other RTX
toxins(15, 26) , the Lys It remains unclear why in the presence of the
same CyaC protein, the CyaA is differently acylated in E. coli and in B. pertussis. One hypothesis is that acylation of
AC toxin is not catalyzed by CyaC itself, but rather that it is
catalyzed by an unidentified transacylase which uses acyl-ACP as
substrate and CyaC as a co-factor. This hypothetical transacylase might
have a slightly different specificity in E. coli and in B.
pertussis. Indeed, the in vitro acylation experiments
involving the HlyA and the CyaC homolog, HlyC, indicated that HlyC is
not a conventional enzyme(27, 28) . In fact,
stoichiometric amounts of HlyC were required for activation of proHlyA.
Moreover, although acyl-ACP and HlyA could be labeled in vitro by a radioactive acyl chain, a radioactive acyl-HlyC intermediate
was not observed. It is conceivable that the transacylating enzyme
might have been present, as a minor component, in the partially
purified preparations of HlyC, proHlyA, and/or acyl-ACP of E.
coli, used for the in vitro acylation system. An
alternative hypothesis is that CyaC may itself be catalyzing the
acylation of CyaA, and when expressed in E. coli, its
specificity may be affected by some alteration in the state of the
overproduced r-proCyaA substrate. The differential effect of altered
acylation on toxin function, namely a reduction in hemolytic activity,
but no effect on invasive activity, provides evidence against the
hypothesis that the pore involved in hemolytic activity has a role in
delivery of the catalytic domain(9, 29) . Since it
appears from their invasive activities that Bp-CyaA and r-CyaA are
comparable in their propensity to insert into the membrane, the
differences in their acylation state must affect a subsequent step in
toxin action. The most likely candidate for this functional defect is
the oligomerization of CyaA molecules to form the hemolytic pore.
Intoxication of target cells occurs as a linear function of AC toxin
concentration(18) , indicating a monomolecular mechanism for
delivery of the catalytic domain. ( The data
suggesting that overacylated r-CyaA is selectively impaired in the
formation of the CyaA channels (Fig. 1) indicate that besides
being essential for the interaction of CyaA with the membrane, the
acylation of CyaA may also be involved in oligomerization of the CyaA
molecules and formation of CyaA channels. It remains to be determined
how the excess acylation on Lys
Volume 270,
Number 35,
Issue of September 01, pp. 20250-20253, 1995
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS AND DISCUSSION
FOOTNOTES
ACKNOWLEDGEMENTS
REFERENCES
)toxin is a bifunctional
177-kDa bacterial protein that contains a calmodulin-activated
adenylate cyclase catalytic domain and a pore-forming domain. It
exhibits a cell-invasive activity by delivering its catalytic domain to
the interior of target cells to elicit supraphysiologic cAMP
accumulation(1, 2, 3, 4) . The
pore-forming capacity of the molecule is responsible for hemolytic
activity against sheep erythrocytes and is entirely independent of the
presence and activities of the catalytic
domain(5, 6, 7, 8, 9) . -amino group of
Lys
(15) . In vitro random chemical
acylation has also been shown to confer limited cell-invasive and
hemolytic activities on CyaA(16) .
Purification of Toxins
The four proteins
evaluated in this study are designated as follows: Bp-CyaA, the native
CyaC-activated AC toxin from B. pertussis; Bp-proCyaA, the
non-activated AC protoxin from strain BPDE386 lacking functional CyaC;
r-CyaA, the recombinant CyaC-activated AC toxin produced in E.
coli; and r-proCyaA, the recombinant non-activated AC protoxin
produced in E. coli lacking CyaC. The E. coli strain
XL1-Blue (Stratagene) was used for expression of r-CyaA from the pCACT3
and for expression of r-proCyaA from pACT7(17, 18) .
Strains BP338 and BPDE386 were used for production of Bp-CyaA and
Bp-proCyaA, respectively(14) .Assays of Adenylate Cyclase Enzymatic, Invasive, and
Hemolytic Activities
Adenylate cyclase enzymatic activity was
measured as described previously(20) . One unit of activity
corresponds to 1 µmol of cAMP formed in 1 min at 30 °C, pH 8.
Hemolytic activity and the cell-invasive activity, which has been shown
to be a good measure of intoxicating activity of CyaAs, were both
determined using sheep erythrocytes (5 10
/ml)
essentially as described(5) .Enzymatic Digestions
Recombinant and B.
pertussis expressed AC toxin preparations were digested with
sequencing grade modified trypsin (Promega) or sequencing grade Asp-N
(Boehringer Mannheim) at an enzyme:substrate ratio of approximately
1:50 (w/w) in Tris adjusted to pH 8.5 for trypsin and 8.0 for Asp-N,
0.2 ml total volume. All digests were carried out for 8 h at 37
°C, adjusted in volume to 0.5 ml with 10% acetonitrile, acidified
with trifluoroacetic acid, and frozen at -40 °C until HPLC
fractionation.
Microbore HPLC and Screening by MALDI-TOF Mass
Spectrometry
All r-CyaA digests and Asp-N digests of Bp-CyaA
were separated with a Polymer Laboratories PLRP-S 8 µm 300 Å
2.1 250 mm column using a reversed-phase binary
gradient(21) . HPLC conditions for the fractionation of the
tryptic fragments derived from Bp-CyaA have also been described
previously(15) . Each fraction was screened for the molecular
mass of the fragments using MALDI-TOF mass spectrometry with an
instrument built in-house(31) , as described
previously(15, 21) . Calculations for predicting
peptide mass values were performed using Mac ProMass. (
)Combined Microcapillary HPLC Electrospray
Ionization Mass Spectrometry
HPLC Fractions from the tryptic
digests which were shown by MALDI-TOF MS to contain peptides which
might possess a posttranslational modification were analyzed further
for amino acid sequence (22, 23) by tandem quadrupole
mass spectrometry using an upgraded TSQ70 instrument with a Finnigan
electrospray source, as described(21) . The molecular masses of
the Asp-N fragments of interest were confirmed by electrospray. To
obtain semi-quantitative estimates of the relative amounts of
palmitoylation versus myristoylation at Lys, and
palmitoylation versus unmodified peptide at Lys
,
the following procedures were used. For the two tryptic acyl peptides
containing Lys
, the relevant HPLC fractions were adjusted
to 100 µl, a 10-µl aliquot removed from each fraction, and the
aliquots pooled into two 1.5-ml microcentrifuge tubes, one containing
the total myristoylated peptide, the other the total palmitoylated
peptide. Each tube was adjusted in volume to 50 µl using a solution
of 10% acetonitrile, 0.1% trifluoroacetic acid. Three replicate
1-µl injections were made using the microcapillary HPLC apparatus
on-line with the TSQ70, as described
previously(15, 21, 23) . For each
determination of the myristoyl peptide, the centroid signals from ions
with +3, +2, and +1 charge states were summed, m/z 532, 797, and 1593. Similarly for the palmitoyl peptide, m/z 541, 811, and 1621 were summed. The average of the three sums was
calculated and the precision estimated by calculating a pooled
RSD(24) . The same approach was used for the
Lys
-containing peptide, summing the five most abundant
charge states for the unmodified Asp-N peptide at m/z 5120,
+5 to +9. For the palmitoylated Asp-N fragment at m/z 5358, the charge states from +4 to +8 were summed.
Synthesis of Analytical Standards
Peptides were
synthesized using automated Fmoc chemistry (25) with a Gilson
422 synthesizer and purified by analytical scale reversed-phase HPLC,
according to a published procedure(21) . The modified peptides
were selectively acylated while still attached to the Wang resin
(Novabiochem) at the -amino group of the desired lysine residue by
the use of
-(1-4,4-dimethyl-2,6-dioxocyclohexylidine)-ethyl--Fmoc-lysine
(Novabiochem)(32) . The purified synthetic peptides were used
to confirm molecular masses, CAD-derived sequence information, and HPLC
retention times.
of CyaA(14, 15) ,
we asked whether or not the difference in the hemolytic activities of
r-CyaA and Bp-CyaA could be accounted for by differences in the
chemical nature and/or location of their posttranslational
modifications.
10
/ml) in TNC (10 mM Tris-HCl, pH 8.0, 150 mM NaCl, 2 mM
CaCl). The suspensions were incubated at 37 °C. After
30 min, aliquots of the suspensions were chilled on ice and washed with
cold TNE buffer (10 mM Tris-HCl, pH 8.0, 150 mM NaCl,
2 mM EDTA). Then L-1-tosylamido-2-phenylethyl
chloromethyl ketone-trypsin was added to 40 µg/ml, and the
suspensions were incubated at 37 °C for 10 min in order to destroy
the AC toxin remaining outside the erythrocytes. Upon addition of
soybean trypsin inhibitor (2-fold excess) the erythrocytes were washed
again, lysed in 50 mM Tris, pH 8.0, 0.2 mM
CaCl, 0.1% Nonidet P-40 and the adenylate cyclase enzymatic
activity, which had penetrated into the erythrocytes and was protected
against externally added trypsin, was measured. The extent of
erythrocyte lysis was determined after 130 min of incubation by
spectrophotometrically measuring the released hemoglobin in cell-free
incubation supernatants at 541 nm. Detergent lysed erythrocyte
suspension was used to determine the 100% lysis
value.
-amino group of
Lys
(15) . As expected, this acylation was
observed only when the toxin was produced in the presence of a
functional CyaC protein and was not observed in
Bp-proCyaA(15) . The pattern of acylation in the r-CyaA,
however, differed from that observed in the B.
pertussis-derived protein. Both palmitoylation (87%) and
myristoylation (13%) were observed at Lys
(n = 3, RSD = 23%). About 67% (n = 3,
RSD = 32%) of the r-CyaA molecules were found to bear a second
modification at Lys
, consisting entirely of
palmitoylation, with the remaining Lys
residues
unmodified (Fig. 2). Acylation at Lys
was also
strictly CyaC-dependent.
residues of r-CyaA are palmitoylated. A,
CAD spectrum of the tryptic fragment of r-CyaA spanning residues
Thr
to Lys
and containing palmitoylation at
Lys
. The parent ion was [M +
2H]
, m/z 941. For definitions of b and
y ions, see (30) . B, MALDI-TOF MS spectrum of the
late eluting microbore HPLC fraction containing palmitoylated
Lys
r-CyaA, observed at m/z 5359 and
encompassing residues Asp
to Gln
(DIASRKGERPALTFITPLAAPGEEQRRRTKTGK
SEFTTFVEIVGKQ),
with a predicted average mass (protonated) of 5358. C,
MALDI-TOF MS spectrum of the fraction containing unmodified Lys
at m/z 5120. The predicted average mass was 5120. The
peaks observed in the MALDI spectra at m/z 4284 and 8566 are
from bovine ubiquitin, which was added to the samples as an internal
standard for mass calibration.
and Lys
of CyaA lie in regions highly conserved among all RTX toxins.
Although acylation of the two corresponding lysine residues of the
homologous E. coli
-hemolysin (HlyA) has been observed in vitro(26) , the pattern of in vivo acylation of the naturally occurring HlyA remains unknown.
Nevertheless, these data led to the suggestion that both Lys and Lys
of CyaA might be acylated(26) .
This, however, appears to be the case only for r-CyaA produced in E. coli and not for the naturally occurring Bp-CyaA produced
by B. pertussis. An abundant tryptic fragment, corresponding
to residues 861-872 of Bp-CyaA, was identified by MALDI-TOF MS
and sequenced by tandem MS (Fig. 3). This fragment would not be
present in tryptic digests if Lys
was acylated, thereby
eliminating the tryptic cleavage site. The tryptic peptide containing
unmodified Lys
and spanning residues Thr
to
Lys
was not recovered by our HPLC
procedures(15, 21) . A weak signal (signal/noise
5) at m/z 1882 was observed by MALDI-TOF, in an HPLC fraction
corresponding to the expected elution time of the tryptic palmitoylated
Lys
-containing peptide. The calculated average mass for
this peptide was 1882.3. The predicted HPLC behavior was based on the
retention times of a synthetic acyl peptide standard (same structure as
that shown in Fig. 2A) and the tryptic acyl peptide
isolated from the Lys
site in r-CyaA (Fig. 2A). The amount recovered from Bp-CyaA was
insufficient to generate a CAD spectrum. Only one abundant Asp-N
fragment was isolated from this site, observed [M +
H]
at m/z 5120, consistent with
unmodified Lys
(see the sequence given in the legend for Fig. 2). Based on the results discussed above, we estimate that
Bp-CyaA palmitoylated at Lys
represents less than 5% of
the total protein.
of Bp-CyaA is
essentially unmodified. CAD spectrum of the unmodified fragment
isolated from a tryptic digest of Bp-CyaA, which could only result from
cleavage at an unmodified Lys
. This fragment spans
residues Ser
to Lys
. The parent ion was
[M + 2H]
, m/z 679.
site of r-CyaA
was also investigated with respect to potential modifications. As was
reported for Bp-CyaA(15) , only unmodified Lys
was observed.
)In contrast,
channel-forming and hemolytic activities are a non-linear function of
toxin concentration exhibiting a cooperativity coefficient suggestive
of a toxin tetramer(8, 18) . On the basis of these
data, we propose that CyaA molecules in different states of
oligomerization, but especially monomers, can deliver their catalytic
domains into cells, whereas oligomerization of AC toxin is a
prerequisite for formation of hemolytic channels. of r-CyaA can impair its
channel-forming activity. Defining this mechanism will contribute to
our general understanding of the role of fatty-acylation in
protein-membrane and protein-protein interactions.
)-9-fluorenylmethoxycarbonyl; HPLC,
high performance liquid chromatography; MALDI-TOF MS, matrix-assisted
laser desorption/ionization time-of-flight mass spectrometry; MS, mass
spectrometry; RSD, relative standard deviation; RTX, repeat in toxin.
))
We thank Teresa Bishop for her help with the
manuscript.
©1995 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:
|
|
 |
|
  N. V. Balashova, D. H. Park, J. K. Patel, D. H. Figurski, and S. C. Kachlany Interaction between Leukotoxin and Cu,Zn Superoxide Dismutase in Aggregatibacter actinomycetemcomitans Infect. Immun., September 1, 2007; 75(9): 4490 - 4497. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Basler, O. Knapp, J. Masin, R. Fiser, E. Maier, R. Benz, P. Sebo, and R. Osicka Segments Crucial for Membrane Translocation and Pore-forming Activity of Bordetella Adenylate Cyclase Toxin J. Biol. Chem., April 27, 2007; 282(17): 12419 - 12429. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. Fiser, J. Masin, M. Basler, J. Krusek, V. Spulakova, I. Konopasek, and P. Sebo Third Activity of Bordetella Adenylate Cyclase (AC) Toxin-Hemolysin: MEMBRANE TRANSLOCATION OF AC DOMAIN POLYPEPTIDE PROMOTES CALCIUM INFLUX INTO CD11b+ MONOCYTES INDEPENDENTLY OF THE CATALYTIC AND HEMOLYTIC ACTIVITIES J. Biol. Chem., February 2, 2007; 282(5): 2808 - 2820. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Basler, J. Masin, R. Osicka, and P. Sebo Pore-Forming and Enzymatic Activities of Bordetella pertussis Adenylate Cyclase Toxin Synergize in Promoting Lysis of Monocytes Infect. Immun., April 1, 2006; 74(4): 2207 - 2214. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. P. Boyd, P. J. Ross, H. Conroy, N. Mahon, E. C. Lavelle, and K. H. G. Mills Bordetella pertussis Adenylate Cyclase Toxin Modulates Innate and Adaptive Immune Responses: Distinct Roles for Acylation and Enzymatic Activity in Immunomodulation and Cell Death J. Immunol., July 15, 2005; 175(2): 730 - 738. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 C. Martin, M.-A. Requero, J. Masin, I. Konopasek, F. M. Goni, P. Sebo, and H. Ostolaza Membrane Restructuring by Bordetella pertussis Adenylate Cyclase Toxin, a Member of the RTX Toxin Family J. Bacteriol., June 15, 2004; 186(12): 3760 - 3765. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
P. J. Ross, E. C. Lavelle, K. H. G. Mills, and A. P. Boyd Adenylate Cyclase Toxin from Bordetella pertussis Synergizes with Lipopolysaccharide To Promote Innate Interleukin-10 Production and Enhances the Induction of Th2 and Regulatory T Cells Infect. Immun., March 1, 2004; 72(3): 1568 - 1579. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Basar, P. Guermonprez, M. Rojas, and C. Leclerc Delivery of CD8+ T-Cell Epitopes into Major Histocompatibility Complex Class I Antigen Presentation Pathway by Bordetella pertussis Adenylate Cyclase: Delineation of Cell Invasive Structures and Permissive Insertion Sites Infect. Immun., January 1, 2000; 68(1): 247 - 256. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Osicková, E. Maier, and R. Benz An Amphipathic alpha -Helix Including Glutamates 509 and 516 Is Crucial for Membrane Translocation of Adenylate Cyclase Toxin and Modulates Formation and Cation Selectivity of Its Membrane Channels J. Biol. Chem., December 31, 1999; 274(53): 37644 - 37650. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.-J. Lee, M. C. Gray, L. Guo, P. Sebo, and E. L. Hewlett Epitope Mapping of Monoclonal Antibodies against Bordetella pertussis Adenylate Cyclase Toxin Infect. Immun., May 1, 1999; 67(5): 2090 - 2095. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Basar, V. Havlicek, S. Bezouskova, P. Halada, M. Hackett, and P. Sebo The Conserved Lysine 860 in the Additional Fatty-acylation Site of Bordetella pertussis Adenylate Cyclase Is Crucial for Toxin Function Independently of Its Acylation Status J. Biol. Chem., April 16, 1999; 274(16): 10777 - 10783. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Gray, G. Szabo, A. S. Otero, L. Gray, and E. Hewlett Distinct Mechanisms for K+ Efflux, Intoxication, and Hemolysis by Bordetella pertussis AC Toxin J. Biol. Chem., July 17, 1998; 273(29): 18260 - 18267. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P. Stanley, V. Koronakis, and C. Hughes Acylation of Escherichia coli Hemolysin: A Unique Protein Lipidation Mechanism Underlying Toxin Function Microbiol. Mol. Biol. Rev., June 1, 1998; 62(2): 309 - 333. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. B. Lim, C. R. B. Walker, L. Guo, S. Pellett, J. Shabanowitz, D. F. Hunt, E. L. Hewlett, A. Ludwig, W. Goebel, R. A. Welch, et al. Escherichia colialpha -Hemolysin (HlyA) Is Heterogeneously Acylated in Vivo with 14-, 15-, and 17-Carbon Fatty Acids J. Biol. Chem., November 17, 2000; 275(47): 36698 - 36702. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Basar, V. Havlicek, S. Bezouskova, M. Hackett, and P. Sebo Acylation of Lysine 983 Is Sufficient for Toxin Activity of Bordetella pertussis Adenylate Cyclase. SUBSTITUTIONS OF ALANINE 140 MODULATE ACYLATION SITE SELECTIVITY OF THE TOXIN ACYLTRANSFERASE CyaC J. Biol. Chem., January 5, 2001; 276(1): 348 - 354. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| All ASBMB Journals | Molecular and Cellular Proteomics |
| Journal of Lipid Research | ASBMB Today |
