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(Received for publication, July 25, 1995) From the
Band 7.2b is an integral membrane phosphoprotein absent from the
erythrocyte membranes of patients with hereditary hydrocytosis, a
hemolytic anemia inherited in an autosomal dominant fashion and
characterized by stomatocytic red blood cells with abnormal
permeability to Na
Hereditary stomatocytosis consists of a heterogeneous group of
disorders characterized by the presence of mouth-shaped (stomatocytic)
erythrocytes on peripheral blood smears. The clinical severity of
hereditary stomatocytosis is variable; some patients experience
hemolysis and anemia, while others are asymptomatic(1) . The
red cell membranes of these patients usually exhibit abnormal
permeability to the univalent cations sodium and potassium, with
resultant modification of intracellular water
content(2, 3, 4, 5) . Hereditary
hydrocytosis is one subset of the stomatocytosis syndromes. Hydrocytic
erythrocytes are characterized by an increased intracellular sodium and
decreased intracellular potassium content(6, 7) . The
transport rate of potassium via both the
Na The red cell membranes
of many hydrocytosis patients lack a 31-kDa protein, band
7.2b(5, 8, 9, 10, 11, 12, 13) .
Band 7.2b is an integral membrane phosphoprotein whose function is not
completely understood. It has been hypothesized that band 7.2b may
support, activate, or regulate an as yet unidentified associated ion
channel(7) . Recent evidence showing a potential interaction
between band 7.2b and the membrane skeleton protein To gain
additional insight into the structure and function of this protein and
provide the necessary tools for further genetic studies of hydrocytosis
patients, we constructed a composite full-length human band 7.2b cDNA
containing the 5`- and 3`-untranslated sequences compared with
previously cloned cDNAs. We also cloned the chromosomal gene encoding
band 7.2b, characterized the genomic structure of the band 7.2b gene,
studied its pattern of expression in different tissues, and identified
its promoter. An imperfect simple sequence repeat (SSR) (
Figure 1:
Structure of the human band 7.2b cDNA.
A diagram of the human band 7.2b cDNA is shown. The open
reading frame is denoted by the box. The locations of the
initiation and termination codons, polyadenylation signals, and an Alu repeat are shown. Sequence obtained by 5` RACE is denoted
by a hatched box. Probes used in genomic library screening and
Northern blotting (see ``Materials and Methods'') are
shown.
Figure 4:
Genomic organization of the human band
7.2b gene. Five overlapping clones containing the band 7.2b gene were
isolated from a human genomic DNA library. These clones spanned a
distance of over 40 kb. A restriction map for EcoRI (E) is shown. Individual exons (not to scale) are denoted by closed boxes. The location of an imperfect simple sequence
polymorphism in the 5`-flanking DNA of the band 7.2b gene is indicated
by an arrow and SSR.
Figure 2:
Mapping the 5` end of the human band 7.2b
cDNA. Primer extension analysis of the 5` end of human band 7.2b mRNA.
Primer extension was carried out using 10 µg of K562, HEL, and HL60
total RNA or tRNA as template. The size of the extension products, 141
nucleotides, indicates that the 5` end of the mRNA is located at
position -61 relative to the adenosine of the initiator
methionine codon. The cDNA sequence of this additional 5`-untranslated
cDNA was determined by 5` RACE and is shown in Fig. 3.
Figure 3:
Nucleotide sequence with encoded amino
acid sequence of human band 7.2b cDNA. The composite nucleotide
sequence shown was determined from 5` RACE products and limited
sequencing of genomic DNA clones. The composite band 7.2b cDNA is 3047
bp in length, predicting a 288-amino acid polypeptide of 31 kDa,
consistent with the mobility previously observed on SDS-polyacrylamide
gel electrophoresis gels. The initiator methionine, ATG, the
termination codon, TAG, and both polyadenylation signals, AATAAA, are underlined. The locations of exons are denoted by triangles.
Secondary structure predictions of the band 7.2b protein predict the
presence of three domains, a highly charged NH
Figure 5:
An Imperfect SSR polymorphism in the human
band 7.2b gene. A, identification of polymorphic alleles using
a PCR-based assay. A SSR was identified in the 5`-flanking DNA of the
band 7.2b gene. Oligonucleotide primers corresponding to sequences
flanking the SSR, one of which was end-labeled with
[
Hereditary xerocytosis, also
known as dehydrated stomatocytosis, is a clinically less severe,
co-dominantly inherited stomatocytic syndrome without band 7.2b
deficiency(6, 7) . The role of band 7.2b in hereditary
xerocytosis, if any, is unknown. We used this polymorphism to study the
two affected homozygous probands of a xerocytosis kindred. The probands
are the products of a consanguineous mating (VI-30 and VI-31 in (34) ) and are presumably homozygous for a single mutation. One
proband was homozygous for the band 7.2b gene common allele(N, N); the
other was heterozygous for alleles N and N + 2, suggesting that a
mutation of the band 7.2b gene is not responsible for the
stomatocytosis observed in this kindred.
Figure 6:
Northern blot Analysis. Top,
samples of 2 µg of poly(A)
Figure 7:
5`-Flanking genomic DNA sequence. The
nucleotide sequence of the 5`-flanking genomic DNA of the human band
7.2b gene is shown. Consensus sequences for potential DNA-protein
binding sites are underlined. The locations of a recognition
sequence for a transcription initiator (InR) site and the initiator
methionine codon are double underlined. The junction between
exon 1 and intron 1 is shown by the inverted
triangle.
To investigate if the region
from -531 to +37 was capable of directing expression of a
reporter gene, test plasmids pHB7-forward or pHB7-reverse (Fig. 8) were transiently transfected into erythroid (K562) or
nonerythroid (NIH3T3) cells. The relative luciferase activity was
determined 24 h after transfection and compared with the activity
obtained with the parental promoterless vector. As shown in Fig. 8, the putative band 7.2b promoter plasmid, pHB7-forward,
directed high level expression of the luciferase reporter gene in both
erythroid and nonerythroid cells. In addition, the plasmid with the
promoter in reverse orientation, pHB7-reverse, also directed expression
in both cell lines but at a lower level, suggesting a bidirectional
capability of the band 7.2b promoter.
Figure 8:
Activity of the band 7.2b gene promoter in
erythroid and nonerythroid cell lines in transient transfection assays.
Plasmids containing 5`-flanking DNA of the band 7.2b gene inserted
upstream of the firefly luciferase gene were transfected into K562 or
NIH3T3 cells as described. Relative luciferase activity was expressed
as that obtained from the test plasmids versus the activity
obtained from the promoterless plasmid pGL2B plasmid, taking into
account the transfection efficiency. The data are means ± S.D.
of at least six independent transfection experiments. The band 7.2b
gene fragment displays bidirectional activity in erythroid and
nonerythroid cells.
The function of band 7.2b protein is unknown. Its importance,
however, is underscored by its wide tissue and species distribution. In
humans, Northern blot analysis detected message in essentially every
tissue analyzed except brain. Protein immunoblotting using a polyclonal
anti-human band 7.2b antibody showed reactivity in human liver and
kidney tissue but none in brain, cardiac tissue, or ileum(12) .
Reactivity to a monoclonal antibody directed against human erythrocyte
band 7.2b has been observed in the erythrocyte membranes of a wide
variety of species including frog, rat, chicken, rabbit, pig, cow, and
sheep(16) . Genetic analyses of patients with hereditary
stomatocytosis (hydrocytosis) have been previously hampered by the lack
of knowledge of the genomic sequences of the band 7.2b gene, including
promoter sequences, as well as by the lack of suitable polymorphic
markers in the gene. Although hereditary hydrocytosis appears to be a
dominantly inherited condition and affected individuals are presumed to
be heterozygous for the disorder, there is complete deficiency of band
7.2b
protein(5, 8, 9, 10, 11, 12, 13) .
This observation suggests a dominant-negative effect, where defective
band 7.2b protein may interact with wild-type band 7.2b protein,
forming an unstable oligomeric protein complex. Band 7.2b protein does
appear to form oligomers. Alternatively, the defect may be present in a
protein that interacts with band 7.2b, with the abnormal interaction
leading to secondary degradation of band 7.2b protein. Band
7.2b-deficient hydrocytosis patients apparently do not suffer any
nonhematologic symptomatology(7) . A variety of mutations
causing human disease have been described that affect RNA processing
and translation (reviewed in (36) ). These mutations may be
associated with dramatic decreases in steady state mRNA levels. This
fact has important implications for mutation detection methods. Reverse
transcriptase-PCR-based techniques are unlikely to detect mutations
with markedly decreased mutant mRNA levels, necessitating study of
these mutations at the level of genomic DNA(36) . A recently
described nonsense mutation in the band 3 gene associated with
decreased mRNA levels, band 3 Noirterre, was not detected using cDNA
mutation detection techniques but was only detected in genomic
DNA(37) . Characterization of the genomic structure of the band
7.2b gene will allow structural studies of the band 7.2b gene in
patients with hereditary hydrocytosis. Cleavage of primary mRNA
transcripts and the addition of poly(A) to the newly formed 3` end of
the transcript downstream of the highly conserved polyadenylation
signal AAUAAA are features of almost all eukaryotic mRNAs(38) .
3`-untranslated regions can have an important influence on mRNA
function including translation, localization, stability, and in some
cases even gene transcription (39) . Alternative
polyadenylation of 3`-untranslated regions may play a role in
determining developmental or tissue-specific preferences for various
mRNA transcripts(39, 40) . The role of the two band
7.2b gene transcripts that vary in their 3`-untranslated regions is
unknown. The bidirectional activity of the band 7.2b gene promoter
is similar to that observed in a wide variety of gene promoters,
particularly housekeeping gene promoters such as those of the genes
encoding dihydrofolate reductase, HMG CoA reductase, and hypoxanthine
phosphoribosyltransferase(41, 42, 43) .
Studies are currently ongoing to further characterize the band 7.2b
gene promoter and to determine if it truly has bidirectional activity.
The nucleotide
sequence(s) reported in this paper has been submitted to the
GenBank(TM)/EMBL Data Bank with accession number(s)
U33925[GenBank],
U33926[GenBank],
U33927[GenBank],
U33928[GenBank],
U33929[GenBank],
U33930[GenBank], and
U33931[GenBank].
Volume 270,
Number 44,
Issue of November 3, 1995 pp. 26358-26363
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
ABSTRACT
INTRODUCTION
MATERIALS AND METHODS
RESULTS
DISCUSSION
FOOTNOTES
ACKNOWLEDGEMENTS
REFERENCES
and K
. The precise
role of band 7.2b is unknown, but it may interact with other proteins
of the junctional complex of the membrane skeleton. To gain additional
insight into the structure and function of this protein and to provide
the necessary tools for further genetic studies of hydrocytosis
patients, we determined the sequence of the full-length human band 7.2b
cDNA, characterized the genomic structure of the band 7.2b gene,
studied its pattern of expression in different tissues, and
characterized the promoter of the gene. The composite band 7.2b gene
cDNA was 3047 base pairs in length. Northern blot analysis revealed a
wide tissue distribution of expression of the band 7.2b gene, with
utilization of alternative polyadenylation signals generating
transcripts of 2.2 and 3.1 kilobases. Cloning of the band 7.2b
chromosomal gene revealed that it is composed of seven exons
distributed over 40 kilobases of DNA. The band 7.2b gene promoter was
identified as a TATA-less, (G + C)-rich promoter with a typical
InR recognition sequence and a single transcription initiation site. It
directed high level expression of a reporter gene in both erythroid and
nonerythroid cells. An imperfect simple sequence repeat polymorphism
was identified in the 5`-flanking DNA, and an assay was developed for
its analysis by PCR.
/K
pump and the
Na
, K
/2Cl
cotransport system is increased. It has been hypothesized that
there is an ion leak in these erythrocytes, with an inadequate
compensatory increase in transport by the
Na
/K
pump.
adducin
suggests that band 7.2b may be a part of the junctional complex of the
membrane skeleton(14) . In this capacity, band 7.2b may
participate in a variety of specialized cellular
functions(15) . Protein immunoblotting has shown the presence
of band 7.2b reactivity in a wide variety of tissues and in a wide
cross-species distribution(12, 16) . The human band
7.2b protein has been purified, and partial cDNAs corresponding to its
coding region have been
cloned(12, 13, 16, 17) . Band 7.2b
shares no sequence homology to other known proteins.
)polymorphism in the band 7.2b gene was identified, and a
PCR-based assay for its analysis was developed.
Genomic Cloning
Human band 7.2b cDNA fragments
corresponding to the 5` end of the coding region (Fig. 1, probe 4) or the 3` end of the coding region (Fig. 1, probe 3) (18) were generated by PCR using primers A
and B or primers C and D (Table 1), respectively, using a human
bone marrow cDNA library (Clontech, Palo Alto, CA) as template. These
fragments were used as hybridization probes to screen a human genomic
DNA library. The library is a Charon 4A bacteriophage library
containing fragments of genomic DNA partially digested with AluI and HaeIII with EcoRI linkers
added(19) . Selected recombinants that hybridized to the
screening probes were purified and subcloned into pGEM-7Z plasmid
vectors (Promega Corp., Madison, WI). Subcloned fragments were analyzed
by restriction endonuclease digestion, Southern blotting, and
nucleotide sequencing.
Nucleotide Sequencing
Nucleotide sequencing was
performed using the dideoxy chain termination method of Sanger et
al. (20) with T7 DNA polymerase (Sequenase, U.S.
Biochemical Corp.). The sequencing primers were the Sp6 or T7 vectors
of the pGEM-7Z plasmid vector or, for some reactions, synthetic
oligonucleotides corresponding to known cDNA sequences (Table 1).
Deoxyinosine triphosphate was substituted for deoxyguanosine
triphosphate to resolve band compressions and ambiguities(21) . Oligonucleotide Synthesis
Oligonucleotides were
synthesized using an automated synthesizer (Applied Biosystems, Foster
City, CA) and purified by oligonucleotide purification column (OPC)
chromatography (Applied Biosystems).RNA Preparation
Total RNA was prepared from human
liver tissue or from the human tissue culture cell lines K562 (chronic
myelogenous leukemia in blast crisis with erythroid characteristics;
ATCC, CCL 243), HEL (erythroleukemia; ATCC, TIB 180), or HL60
(promyelocytic leukemia; ATCC, CCL 240) using the
guanidinium-thiocynate-chloroform method as described(22) .Primer Extension Analyses
The transcription start
site of the band 7.2b gene was determined using primer extension
analysis. Primers B or E (Table 1) were used in primer extension
reactions as described(23) . Templates in these reactions were
10 µg of total RNA from the human cell lines K562, HEL, and HL60 or
tRNA.5` Rapid Amplification of cDNA Ends (RACE)
1
µg of total human liver RNA was reverse transcribed using primer E (Table 1) and avian myeloblastosis virus reverse transcriptase
(Promega Corp.). Single-stranded oligonucleotide ligation and PCR
amplification were carried out as described using primers B and
E(24, 25) . Amplification products were subcloned and
sequenced.Detection of a Polymorphism of the Band 7.2b
Gene
An imperfect SSR polymorphism was identified in the
5`-flanking DNA of the band 7.2b gene (see below), and an assay for
this polymorphism was developed. Oligonucleotide primers I and J (Table 1), corresponding to sequences that flank the SSR, were
synthesized for use in PCR. Primer I was end-labeled with
[P]ATP using polynucleotide kinase. PCR
amplification was carried out using labeled primer I and unlabeled
primer J with
100-250 ng of genomic DNA/reaction as
template. Amplification conditions were as follows: denaturation at 94
°C for 45 s, annealing at 60 °C for 45 s, and extension at 50
°C for 45 s; 25 cycles of amplification were performed.
Amplification products were mixed 1:1 with formamide-based loading dye,
heated to 94 °C for 5 min, and then electrophoresed in a 6%
acrylamide gel. After electrophoresis, the gel was dried, and
autoradiography of the gel for 6 h at -80 °C using an
intensifying screen was performed.
Northern Blot Analyses
Multiple-tissue Northern
blots containing 2 µg of poly(A) mRNA/tissue were
obtained from Clontech. The locations of probes used in Northern
blotting are shown in Fig. 1. Probe 1 was obtained by PCR
amplification of human bone marrow cDNA using primers D + F (Fig. 1). Probe 2 is a 0.7-kb EcoRI fragment present in
the 3`-untranslated region of the band 7.2b gene. A 2.0-kb human
-actin cDNA probe was used as a control for loading in Northern
blot analyses(26) .Cell Culture
Two cell lines, K562 (erythroid) and
NIH3T3 (murine fibroblast, nonerythroid) were used to study expression
of the putative promoter of the band 7.2b gene. K562 cells were
maintained in RPMI 1640 medium containing 10% fetal calf serum. NIH3T3
cells were maintained in Eagle's minimal essential medium
supplemented with 10% fetal calf serum.Preparation of Reporter Plasmids
A 568-bp DNA
fragment corresponding to -531 to +37 bp of the band 7.2b
gene 5`-flanking DNA was amplified using primers G and H (Table 1) and genomic clone 13 DNA (see Fig. 4) as
template. Test plasmids were prepared by inserting the amplified DNA
fragment upstream of the firefly luciferase reporter gene in the
plasmid pGL2B (Promega Corp.) in both orientations. These plasmids were
designated pHB7-forward and pHB7-reverse, respectively. All test
plasmids were sequenced to exclude cloning or PCR-generated artifacts.
Transient Transfection Analyses
All plasmids
tested were purified using Qiagen columns (Qiagen, Inc., Chatsworth,
CA), and at least two preparations of each plasmid were tested.
10
K562 cells were transfected by electroporation with a
single pulse of 300 V at 960 microfarads with 20 µg of test plasmid
and 0.5 µg of pCMV, a mammaliam reporter plasmid expressing
-galactosidase driven by the human cytomegalovirus immediate early
gene promoter (Clontech). 10
NIH3T3 cells were transfected
with 2.0 µg of test plasmid and 0.25 µg of the pCMV
plasmid by lipofection using 4 µl of Lipofectamine (Life
Technologies, Inc.). Twenty-four hours after transfection, cells were
harvested and lysed, and the activity of both luciferase and
-galactosidase activity was determined in cell extracts. All
assays were performed in triplicate. Differences in transfection
efficiency were determined by co-transfection with the pCMV
plasmid.Computer Analyses
Computer-assisted analyses of
derived nucleotide and predicted amino acid sequences were performed
utilizing the sequence analysis software package of the University of
Wisconsin Genetics Computer Group (UW GCG; Madison, WI) (27) and the BLAST algorithm (National Center for Biotechnology
Information, Bethesda, MD)(28) .
Mapping the 5` End of the Human Band 7.2b
cDNA
To identify the 5` end of the human band 7.2b cDNA, primer
extension experiments were performed. These experiments (Fig. 2)
predicted the presence of an additional 61 bp in the mRNA upstream from
the putative initiator codon, previously identified in cDNA cloning.
These additional 61 bp of upstream 5`-untranslated sequence were
obtained by 5` RACE ( Fig. 1and Fig. 3). These sequences
agreed with the 17 of 21 nucleotides of 5`-untranslated sequence
previously reported(13) . Sequences obtained by RACE were
verified by comparison to corresponding genomic DNA sequences (see
below). The sequences around the translational start site match
important consensus sequences, A at -3 and G at
+4(29) . No additional ATGs were present in the
5`-untranslated sequences. Taken together, these data suggest that this
sequence is at or very near the 5` end of the human band 7.2b cDNA.
Cloning of Chromosomal Gene: Isolation and Analysis of
Recombinant Clones
Primary screening of a human genomic DNA
library with a cDNA probe yielded over a dozen hybridization-positive
plaques. Selected recombinants were analyzed, and five overlapping
clones were identified that spanned 40 kb of DNA containing the band
7.2b gene. An EcoRI restriction map of this 40-kb region is
shown in Fig. 4.Mapping the Exon/Intron Junctions of the Band 7.2b
Gene
The human band 7.2b gene is encoded by seven exons (Table 2). Five of the seven exons are relatively small, 135 bp
or less in length, with two of the exons (73 and 82 bp) at the the
lower limit usually observed for exon size(30) . The first and
seventh exons contain untranslated sequences; the 5`-untranslated
region is 61 bp in length, and the 3`-untranslated is 2120 bp in
length. Comparison of the exon/intron boundaries with reported
consensus sequences reveals that the ag:gt rule was not violated at any
splice junction(31, 32) . There are no AG
dinucleotides within the 15 bp upstream of the 3` (acceptor) splice
junctions. There is an Alu repeat in reverse orientation in
the 3`-untranslated region from positions 1373 to 1675 of the cDNA that
is 83% similar to a consensus Alu sequence(33) .
-terminal
domain, a hydrophobic stretch that encodes a potential
membrane-spanning domain, and a COOH-terminal domain composed of
sheet and 
helix. There is no concordance between the exon
organization of the gene and the location of these three domains in the
protein.Variations in the Band 7.2b Gene and the cDNA
Sequence
There were two differences between the cDNA sequences
reported by Hiebl-Dirschmied et al.(17) and Stewart et al. (7) GC or CG, at positions +76/77, respectively.
Analysis of the genomic DNA revealed the sequence GC at this location,
encoding a histidine, CAC, not asparagine, GAC. The 3`-untranslated
region of the cDNA sequence shown in Fig. 3contains multiple
differences compared with the previously reported sequence. These
differences probably represent sequencing errors.Identification and Characterization of a Polymorphism of
the Band 7.2b Gene
An imperfect SSR polymorphism was identified
approximately 11 kb 5` to exon 1 in the 5`-flanking DNA of the gene (Fig. 4). An assay for this polymorphism was developed using
oligonucleotide primers (I and J, Table 1) corresponding to
sequences flanking the SSR in PCR amplification. Study of the
polymorphism using this PCR-based assay in 126 alleles from 63
unrelated individuals from diverse racial backgrounds detected five
different alleles (Fig. 5A). Sequence analysis of these five
alleles revealed various deletions or insertions (Fig. 5B).
Allelic frequencies are shown in Table 3. This is the first DNA
polymorphism of the band 7.2b gene to be identified. This intragenic
band 7.2b gene polymorphism will facilitate linkage analysis studies in
families with hereditary hydrocytosis.
P]ATP, were used to amplify genomic DNA in a
PCR reaction. Amplification products were denatured and electrophoresed
in an acrylamide gel, the gels were autoradiographed, and the results
were analyzed. Five alleles of varying size were identified in
individuals from different racial backgrounds using this PCR-based
assay of genomic DNA, with the most common allele arbitrarily called N. B, sequence of the imperfect simple sequence repeat.
Differences in the sequences of the five identified alleles are shown.
The most common allele is denoted as N.
Band 7.2b mRNA Exhibits Wide Tissue Distribution of
Expression
Northern blot analysis using probe 1 (Fig. 1)
detected an abundant mRNA of 3.1 kb in all tissues examined except
brain, colon, and ovary (Fig. 6A). A 2.2-kb signal was also
detected in most tissues but in lesser amount compared with the 3.1-kb
mRNA, particularly in spleen, where almost no 2.2-kb signal was
observed.
RNA from various human
tissues were hybridized to a [
P]dCTP-labeled
cDNA fragment (probe 1). Abundant message was detected in all tissues
examined except brain, colon, and ovary. Middle, the same
blots were stripped and rehybridized to probe 2. Bottom, the
same blots were stripped and hybridized with a 2.0-kb human
-actin
cDNA probe as a control for loading.
Alternate Polyadenylation of the Band 7.2b
mRNA
Polyadenylation signals are located at positions
2034-2039 bp and 3012-3026 bp in the 3`-untranslated region
of the cDNA. To determine if both polyadenylation signals are utilized,
Northern blots were hybridized to cDNA sequences upstream and
downstream of the 5` polyadenylation signal(2034-2039). While
Northern blots clearly show the presence of two transcripts of 2.2 and
3.1 kb in length when the upstream probe 1 is used, only a transcript
of 3.1 kb is detected when the downstream probe 2 (Fig. 1) is
hybridized to the same Northern blots (Fig. 6B). Thus
these transcripts are most likely the result of alternate
polyadenylation. In contrast, the murine band 7.2b gene does not
apparently undergo alternative polyadenylation(25) .The Human Band 7.2b Gene Promoter Is Active in Erythroid
and Nonerythroid Cells
The nucleotide sequence of the
5`-flanking genomic DNA upstream of the human band 7.2b cDNA
transcription start site is shown in Fig. 7. Inspection of the
sequences reveals features characteristic of a housekeeping gene
promoter including lack of consensus TATA or CCAAT sequences and a high
G + C content (68%, between positions -1 and -334). A
recognition sequence for a transcription initiator (InR),
CATTCC, (35) is double underlined. Consensus
sequences for a number of potential DNA-binding proteins, including
multiple potential Sp1 binding sites, are also present in the
5`-flanking sequences (Fig. 7).
Computer Analyses
When compared with sequences
present in available data bases, there was no significant homology
between the band 7.2b gene sequence and that of other genes or proteins
(other than the mouse band 7.2b gene and protein). Searching using only
the highly charged 25 amino acid NH terminus also failed to
reveal any significant homologies.
)
We thank Dr. George Segal for providing blood samples
from the family with hereditary xerocytosis and C. Wong and L.
Lozovatsky for skilled technical assistance.
©1995 by The American Society for Biochemistry and Molecular Biology, Inc.
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B. D. Smith and G. B. Segel Abnormal Erythrocyte Endothelial Adherence in Hereditary Stomatocytosis Blood, May 1, 1997; 89(9): 3451 - 3456. [Abstract] [Full Text] [PDF]
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