A Novel Labeling Approach Supports the Five-transmembrane Model
of Subunit a of the Escherichia coli ATP
Synthase*
Takaaki
Wada,
Julie C.
Long,
Di
Zhang, and
Steven B.
Vik
From the Department of Biological Sciences, Southern Methodist
University, Dallas, Texas 75275
 |
ABSTRACT |
Cysteine mutagenesis and surface labeling has
been used to define more precisely the transmembrane spans of subunit
a of the Escherichia coli ATP synthase. Regions
of subunit a that are exposed to the periplasmic space have
been identified by a new procedure, in which cells are incubated with
polymyxin B nonapeptide (PMBN), an antibiotic derivative that partially
permeabilizes the outer membrane of E. coli, along with a
sulfhydryl reagent, 3-(N-maleimidylpropionyl) biocytin
(MPB). This procedure permits reaction of sulfhydryl groups in the
periplasmic space with MPB, but residues in the cytoplasm are not
labeled. Using this procedure, residues 8, 27, 37, 127, 131, 230, 231, and 232 were labeled and so are thought to be exposed in the periplasm.
Using inside-out membrane vesicles, residues near the end of
transmembrane spans 1, 64, 67, 68, 69, and 70 and residues near the end
of transmembrane spans 5, 260, 263, and 265 were labeled. Residues 62 and 257 were not labeled. None of these residues were labeled in
PMBN-permeabilized cells. These results provide a more detailed view of
the transmembrane spans of subunit a and also provide a
simple and reliable technique for detection of periplasmic regions of
inner membrane proteins in E. coli.
 |
INTRODUCTION |
The ATP synthase from Escherichia coli is typical of
the ATP synthases found in mitochondria, chloroplasts, and many other bacteria (for reviews, see Refs. 1-3). It contains an F1
sector, with subunits for nucleotide binding and catalysis, and an
F0 sector, which conducts protons across the membrane. Five
different subunits are found in the E. coli F1:
,
,
,
, and
, in a stoichiometry of 3:3:1:1:1. Three
different subunits named a, b, and c
form the E. coli F0 with a stoichiometry of
1:2:12 (4).
The mechanism by which an electrochemical proton gradient across the
membrane drives ATP synthesis is thought to involve a rotary mechanism.
The crystallization of F1 from bovine mitochondria (5) led
to a high resolution structure of the
3
3
hexamer, plus parts of
in the central core.
Subsequently, the hypothesis of rotation of
and
and relative to
3
3 has been supported by direct
visualization of rotation of fluorescently labeled actin filaments
covalently attached to
(6) or
(7). It has been proposed that
F0 subunit c drives the rotation of
and
as a rotor (8), whereas subunits a and b function
as the stator. Recent theoretical work has indicated the feasibility of
this proposal (9), but as of yet there is no direct evidence of rotation by F0 subunits.
Information about the tertiary and quaternary structure of
F0 subunits will be necessary for an understanding of how
F0 translocates protons, and how it might drive rotation of
and
subunits in F1. Subunit b seems to
be embedded in the membrane via a span of hydrophobic amino acids at
its N terminus. A truncated, soluble form of b has been
shown to be extended and dimeric (10). Recent NMR studies
of c have confirmed the
-helical hairpin structure of the
two predicted transmembrane spans, and also details of the essential
residue Asp61 and its local environment (11, 12). Cysteine
cross-linking studies have provided information about the oligomeric
structure of subunit c (13) and about its interactions with
subunit a (14). One face of a transmembrane
-helix
between residues 207 and 225 of subunit a appears to be in
contact with the oligomer of subunit c. This region includes
Arg210, which is thought to be essential for function
(15-17).
The transmembrane topology of subunit a has been analyzed by
several methods in recent years. In particular, studies using the
labeling of cysteine substitutions (18, 19), epitope insertions (20),
and peptide-directed antibodies (20, 21), to identify surface
accessible regions of the protein have come to significant agreement.
However, the location of the N terminus remains controversial, leading to models of five- or six-transmembrane spans. Studies using
the labeling of cysteine substitutions (18, 19) concluded five-transmembrane spans, with a periplasmic N terminus. Studies using
epitope insertion and peptide-directed antibodies (20, 21) found
cytoplasmic localization of the N terminus, leading to
six-transmembrane spans. All of the studies required the preparation of
oriented membrane vesicles for probing potentially accessible surface
residues or regions. A limitation of such experiments is that the
membrane vesicles may not be perfectly sealed or oriented. Also, some
reagents may be somewhat permeable to membranes because of a limited
degree of partitioning into the lipid phase. Such limitations may be
responsible for the detection of certain residues or epitopes in
membrane vesicles of both orientations.
In this study, we have minimized these problems for the detection of
periplasmic regions of inner membrane proteins of E. coli.
This procedure requires the use of an antibiotic derivative, PMBN,1 to partially
permeabilize the outer membrane (22) to the labeling reagent, MPB.
Essentially zero background labeling is seen with highly accessible
cytoplasmic cysteine residues, allowing a more definitive assignment of
periplasmic regions.
 |
EXPERIMENTAL PROCEDURES |
Materials--
Restriction endonucleases and T4 DNA ligase were
obtained from New England Biolabs. Materials for silver sequencing and
plasmid mini-preps were obtained from Promega Corp. Synthetic
oligonucleotides were obtained from Operon Technologies. Urea was from
International Biotechnologies, Inc. MPB was obtained from Molecular
Probes. PMBN, mouse and rat anti-HA, anti-His tag antibody, and
proteins A and G-agarose were obtained from Roche Molecular
Biochemicals. Ni-NTA resin was obtained from Qiagen. Talon resin was
obtained from CLONTECH. Octyl glucoside was
obtained from Sigma or Anatrace. Anti-a antiserum was
provided by Dr. Karlheinz Altendorf (Universität Osnabrück). Immunoblotting reagents were obtained from
Bio-Rad.
Growth and Expression--
For expression, RH305
(uncB205, recA56, srl::Tn10,
bglR, thi-1, rel-1, Hfr PO1) was used
as the background strain (23). It produces a defective
subunit a that is truncated near Pro240
(24), and is complemented by plasmids containing a wild
type uncB gene. Cultures were grown at 37 °C in LB or
Minimal A medium supplemented with succinate (0.2%). Media were also
supplemented with chloramphenicol (34 mg/liter) or tetracycline
(12.5 mg/liter) as appropriate.
Plasmids and Mutagenesis--
New mutations were constructed by
cassette mutagenesis (25) and are shown in Table
I. All mutants, when expressed in RH305, permitted growth on succinate minimal medium, indicating normal ATP
synthesis, with the exception of S62C. Plasmids designated "His"
code for five additional histidine residues following the natural
C-terminal His271 of subunit a. Plasmids
designated "HisHA," contain, in addition to the histidine segment,
the nine-residue HA epitope (underlined) inserted after
Ser268. It generates a C-terminal sequence of
YPYDVPDYASEEHHHHHH, with an additional Ser residue
following the HA epitope. One new plasmid was constructed for this
study, pARP2-HisHA. First, a 600-bp BglI-AflII fragment was isolated from pSBV10 (26), internal to uncB.
This fragment was ligated to a 2700-base pair
BglI-AflII fragment from pTW1-HisHA (18) to form
pARP1-HisHA. A 115-bp SpeI-BglI fragment was
excised from pARP1-HisHA and replaced by synthetic DNA to generate
pARP2-HisHA. The construction of the other cysteine mutations at
residues 8, 27, 69, 128, and 131, was described previously (18). These
mutations were all expressed with His-HA tags at the C terminus.
Preparation and Labeling of Membrane Vesicles--
Inside-out
membrane vesicles were prepared by French press as described previously
(18). The membrane vesicles were labeled in 120 µM MPB
for 15 min at 25 °C, as described previously (18). After labeling,
subunit a was detergent extracted and purified by Ni-NTA, as
described previously (18).
Preparation and Labeling of Whole Cells--
A 30-ml culture of
cells was grown in LB medium at 37 °C to A600 = 1.0 and harvested. The cells were resuspended in 1 ml of 20 mM K-Mops, 250 mM KCl, 1 mM
MgSO4, pH 7.0, and washed twice. For labeling, they were
immediately suspended in the same buffer with 50 µM PMBN
and 150 µM MPB and incubated at 25 °C for 1 h. Following centrifugation (10 min at 16,000 × g), the
cells were resuspended in 20 mM Tris-HCl, pH 7.5, 1.5%
octylglucoside, 0.1% deoxycholate, 0.5% cholate, and 1% Tween 20. Following a 2-h incubation at 4 °C, the previous centrifugation step
was repeated, and the supernatant fraction was transferred to a new
microfuge tube and mixed with 50 µl of protein A-agarose and
incubated another 3 h (4 °C). After a short spin to remove
agarose, the supernatant fraction was transferred to a new microfuge
tube and mixed with 100 µg of anti-HA and incubated another 1.5 h (4 °C). Finally, 50 µl of protein A-agarose was added, incubated
for 3 h (4 °C), washed and suspended in 100 µl of 50 mM Tris-HCl, pH 6.8, 2% SDS, 25% glycerol, 14.4 mM 2-mercaptoethanol, and 0.1% bromphenol blue.
MPB Detection and Immunoblotting--
Samples of purified
subunit a were subjected to SDS-polyacrylamide gel
electrophoresis (13% acrylamide) and transferred to nitrocellulose
membrane (0.2 µm) as described previously (18). Subunit a
detection, using rabbit anti-a serum, was carried out as
described previously (18). Subunit a bearing the HA epitope was detected with rat anti-HA in a similar manner. The use of rat
anti-HA eliminated detection of the mouse anti-HA, present in the
immunoprecipitation complex, after reaction with secondary antibodies.
 |
RESULTS |
A model for subunit a of the ATP synthase containing
five-transmembrane spans has been presented recently from labeling
studies of cysteine mutants (18). In this study, 24 new cysteine
substitution mutants have been constructed to define more precisely the
ends of the transmembrane spans. Periplasmic exposure of the cysteine residues was detected by labeling with a new procedure in which cells
were partially permeabilized by incubating with 50 µM
polymyxin B nonapeptide in the presence of the sulfhydryl reagent MPB.
During this procedure, only periplasmic residues were labeled. Labeling was also performed with inside-out membrane vesicles prepared by French
press. Cytoplasmic residues were identified as those that can be
labeled in inside-out membrane vesicles but not in PMBN-permeabilized
cells. Both labeling procedures were carried out for each cysteine
mutant, and the results are organized into five groups.
In Fig. 1, the results for residues 37, 39, and 44 are shown, along with previously studied cysteine mutants 8 and 27. In panel A, labeling in PMBN-permeabilized cells is
shown, and in panel B, labeling in inside-out membrane
vesicles is shown. Panel C shows immunoblots of the membrane
vesicles using rat anti-HA antibody. Residues 8 and 27 were shown
previously to be periplasmic (18), although other methods have
indicated that the N terminus is cytoplasmic (20, 21). Here these
residues are labeled in PMBN-permeabilized cells (Fig. 1A),
and also in inside-out membrane vesicles (Fig. 1B), because
of the permeability of MPB under these conditions. Residue 37 is
labeled in a similar pattern but not as strongly. Residues 39 and 44 are not labeled by either method.

View larger version (58K):
[in this window]
[in a new window]
|
Fig. 1.
Labeling of residues 8-44 in subunit
a. The first lane on the
left contains molecular mass standards, 28 and 36 kDa. The
migration of subunit a is indicated to the right.
The residues changed to Cys are indicated by number
above each lane. Panel A shows
labeling of cysteine residues by MPB in PMBN-permeabilized cells, as
detected by avidin-conjugated alkaline phosphatase color assay.
Panel B shows labeling of cysteine residues by MPB in
inside-out membrane vesicles, as detected by the same color assay.
Panel C shows an immunoblot of the samples from panel
A, using rat anti-HA for detection of subunit a.
|
|
The C-terminal end of the first transmembrane span was probed by
cysteine substitution of residues 62, 64, 67, 68, 69, and 70, and the
results are shown in Fig. 2. None of
these mutants can be labeled by MPB in PMBN-permeabilized cells (Fig.
2A), whereas all but 62 can be labeled in inside-out
membrane vesicles (Fig. 2B). Residues 67, 68, 69, and 70 are
labeled strongly, compared with residue 64. These results indicate
cytoplasmic exposure for residues 64, 67, 68, 69, and 70. The mutant
S62C is impaired in function as indicated by little or no growth in
minimal succinate medium, but immunoblots indicate the presence of the
protein in membrane preparations at a significant level (Fig.
2C).

View larger version (50K):
[in this window]
[in a new window]
|
Fig. 2.
Labeling of residues 62-70 in subunit
a. The first lane on the
left contains molecular mass standards, 28 and 36 kDa. The
migration of subunit a is indicated to the right.
The residues changed to Cys are indicated by number
above each lane. Panel A shows
labeling of cysteine residues by MPB in PMBN-permeabilized cells, as
detected by avidin-conjugated alkaline phosphatase color assay.
Panel B shows labeling of cysteine residues by MPB in
inside-out membrane vesicles, as detected by the same color assay.
Panel C shows an immunoblot of the samples from panel
A, using rat anti-HA for detection of subunit a.
|
|
The periplasmic loop between transmembrane spans 2 and 3 was probed by
cysteine substitution at positions 127, 128, and 131, and the results
are shown in Fig. 3. Residue 131, consistent with earlier results (18, 19), can be labeled in
PMBN-permeabilized cells, indicating periplasmic exposure. Residue 127 is labeled similarly, whereas residue 128 is resistant to labeling. All
three residues are labeled somewhat in inside-out membrane vesicles (Fig. 3B).

View larger version (62K):
[in this window]
[in a new window]
|
Fig. 3.
Labeling of residues 127-131 in subunit
a. The first lane on the
left contains molecular mass standards, 28 and 36 kDa. The
migration of subunit a is indicated to the right.
The residues changed to Cys are indicated by number above
each lane. Panel A shows labeling of cysteine
residues by MPB in PMBN-permeabilized cells, as detected by
avidin-conjugated alkaline phosphatase color assay. Panel B
shows labeling of cysteine residues by MPB in inside-out membrane
vesicles, as detected by the same color assay. Panel C shows
an immunoblot of the samples from panel A, using rat anti-HA
for detection of subunit a.
|
|
The periplasmic loop between transmembrane spans 4 and 5 was probed by
cysteine substitution at positions 226-228, 230-234, 240, 241, 244, and 246. These results are shown in Fig.
4. Only residues 230, 231, and 232 were
labeled by MPB in PMBN-permeabilized cells (Fig. 4A),
indicating a very limited periplasmic exposure in this region. None of
the residues were labeled in inside-out membrane vesicles (Fig.
4B).

View larger version (36K):
[in this window]
[in a new window]
|
Fig. 4.
Labeling of residues 226-246 in subunit
a. The first lane on the
left contains molecular mass standards, 28 and 36 kDa. The
migration of subunit a is indicated to the right.
The residues changed to Cys are indicated by number above
each lane. The double mutant S233C,Q234C is indicated by
233/4. Panel A shows labeling of cysteine
residues by MPB in PMBN-permeabilized cells, as detected by
avidin-conjugated alkaline phosphatase color assay. Panel B
shows labeling of cysteine residues by MPB in inside-out membrane
vesicles, as detected by the same color assay. Panel C shows
an immunoblot of the samples from panel A, using rat anti-HA
for detection of subunit a.
|
|
The C-terminal end of the fifth, and last, transmembrane span was
probed by cysteine substitution at positions 257, 260, 263, and 265, and the results are shown in Fig. 5. None
of these residues was labeled in PMBN-permeabilized cells (Fig.
5A). All but 257 were labeled in inside-out membrane
vesicles (Fig. 5B), indicating cytoplasmic exposure for
approximately twelve residues at the C terminus of subunit
a.

View larger version (59K):
[in this window]
[in a new window]
|
Fig. 5.
Labeling of residues 257-265 in subunit
a. The first lane on the
left contains molecular mass standards, 28 and 36 kDa. The
migration of subunit a is indicated to the right.
The residues changed to Cys are indicated by number above each
lane. Panel A shows labeling of cysteine residues
by MPB in PMBN-permeabilized cells, as detected by avidin-conjugated
alkaline phosphatase color assay. Panel B shows labeling of
cysteine residues by MPB in inside-out membrane vesicles, as detected
by the same color assay. Panel C shows an immunoblot of the
samples from panel A, using rat anti-HA for detection of
subunit a. The residues changed to Cys are indicated by
number above each lane. Constructs for Y263C and
S265C do not contain the HA-epitope.
|
|
 |
DISCUSSION |
A new method for determining the orientation of inner membrane
proteins in Escherichia coli has been described. This method is based upon a procedure described by Matos et al. (27), in which E. coli cells were partially permeabilized with EDTA
to permit periplasmic labeling of cysteine mutants of an inner membrane transport protein. In this study, PMBN (22) has been used in place of
EDTA for more efficient labeling of subunit a of the ATP
synthase. PMBN is not essential for the labeling of some residues by
MPB, e.g. E131C. This suggests that MPB has a limited,
intrinsic permeability with respect to the outer membrane. In addition, the detection of labeled subunit a after labeling in whole
cells requires a reliable purification procedure, to eliminate
background labeling. That is an essential step because subunit
a cannot be expressed to high levels. These results
demonstrate that immunoprecipitation of subunit a, tagged
with the HA epitope, by the commercial mouse anti-HA provides a cleaner
background than does a procedure using Ni-NTA chromatography.
The results indicate that during permeabilization of E. coli
outer membrane by PMBN, only residues of subunit a that are
facing the periplasm are exposed to the sulfhydryl reagent MPB. For
example, mutant S69C, which labels strongly in inside-out membrane
vesicles prepared by French press, is not labeled in whole cells
permeabilized by PMBN. This indicates that the concentration of the
reagent MPB does not build up inside the cell to levels that are high enough for significant reaction with S69C. This feature distinguishes this method from other methods in which labeling of membrane proteins occurs in oriented membrane vesicles. In such preparations, residues that are labeled strongly in one orientation, are generally labeled in
the opposite orientation, to a lesser extent. Also, this method does
not seem to label within transmembrane spans, as indicated by the lack
of labeling in residues 233-246. Therefore, the method introduced here
allows a more definitive analysis of the orientation of membrane
proteins in E. coli, and eliminates the need for the preparation of right-side-out membrane vesicles.
The results presented here provide support for the five-transmembrane
model of subunit a of the ATP synthase, presented recently (18, 19). They also define better, the periplasmic loops and the
cytoplasmic ends of the first and last transmembrane spans. These
results are summarized in Fig. 6.

View larger version (61K):
[in this window]
[in a new window]
|
Fig. 6.
Transmembrane model of subunit a
of the E. coli ATP synthase. Residues that
cannot be labeled by MPB when changed to cysteine are indicated by
thicker circles. They include residues 18, 39, 44, 62, 89, 128, 226, 227, 233, 234, 238, 240, 241, 244, 246, and 257. Residues
that can be labeled by MPB when changed to cysteine are indicated by
black filled circles. Those that can be labeled in
PMBN-permeabilized cells include 8, 27, 37, 127, 131, 230, 231, and
232. They are placed on the periplasmic face. Those that are labeled in
inside-out membrane vesicles, but not in PMBN-permeabilized cells,
include 64, 67, 68, 70, 260, 263, and 265. They are placed on the
cytoplasmic face. The HA epitope is indicated by the nine shaded
residues near the C terminus. The terminal residue of each
transmembrane span is numbered. Results from previous work
(18)2 are included.
|
|
The first transmembrane span is well defined by the labeling results,
indicating that it occurs between residues 37 and 64. The first
cytoplasmic loop is highly exposed in a region extending from residue
64 to 70. The first periplasmic loop is not as highly exposed, but more
work will be necessary to define this region. Residues following 131 have not been tested, and so the start of the third transmembrane span
remains uncertain. Previous labeling of residues G172C (18) and K169C
(19) indicates the probable cytoplasmic end of the third span. The
second periplasmic loop has been extensively examined in this study. Of
twelve residues tested, only three consecutive residues, 230-232,
could be labeled. Furthermore, the extent of labeling of each was low,
compared with residues near the N terminus, indicating rather limited
exposure in this region of the protein. The cytoplasmic end of the
fifth transmembrane span was defined by the labeling of residues 260, 263, and 265, but not 257. Previous work had identified residue 266 as
cytoplasmic (19).
For function, the only essential residue of subunit a seems
to be Arg210, which is thought to interact with the
essential Asp61 of subunit c. This has been
supported (14) by analysis of engineered disulfide cross-links formed
between subunit a and subunit c, which indicated
that a face of subunit a between residues 207 and 225 lies
opposed to residues 55-73 in subunit c. The results presented here suggest that Arg210 is located closer to the
cytoplasmic surface than the periplasmic surface of the protein. This
should be verified by more labeling studies in the region of the
protein preceding residue 210. Results so far indicate that residue 196 can be labeled, but not residue 202 (19).
Two other residues have been implicated in the function of subunit
a, His245 and Glu219.
Glu219 can tolerate a limited range of amino acid
substitutions, and cysteine mutants of both Glu219 and
His245 can be suppressed by second-site mutations in
subunit a, A145E and D119H, respectively (15). Results
presented here indicate that these residues are not highly
accessible to the periplasm. However, the possibility of a short,
water-filled channel that is not accessible to the much larger MPB
cannot be ruled out.
In summary, the periplasmic location of the N terminus of subunit
a is strongly supported by the results presented here.
Residues 8, 27, and 37 are clearly labeled in PMBN permeabilized cells. These residues, along with residues 3 and 24, previously described, and
residues 14, 15, and 172
indicate extensive exposure in the periplasm of the N-terminal region
of subunit a. Contradictory results have been reported in
two other studies using antibodies for detection (20, 21). It was
reported that antibodies generated against an N-terminal peptide and
that monoclonal antibodies raised against purified subunit a
that have epitopes within the N-terminal region both preferentially
recognize right-side-out membrane vesicles over inside-out vesicles. At
present, there is no simple explanation as to why both antibody
procedures contradict the results presented here and elsewhere. One
important difference may be the simplicity of the procedure described here.
 |
ACKNOWLEDGEMENTS |
We thank Dr. K. Altendorf (Universitt
Osnabrck) for generously providing anti-a antiserum and Dr.
P. Maloney (Johns Hopkins University) for helpful discussions.
 |
FOOTNOTES |
*
This work was supported by United States Public Health
Service Grant GM40508 from the National Institutes of Health, and by the Welch Foundation.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.
To whom reprint requests should be addressed. Tel.: 214-768-4228;
Fax: 214-768-3955; E-mail: svik{at}mail.smu.edu.
2
A. R. Patterson, T. Wada, and S. B. Vik, submitted for publication.
 |
ABBREVIATIONS |
The abbreviations used are:
PMBN, polymyxin B
nonapeptide;
MPB, (N-maleimidylpropionyl) biocytin;
anti-HA, monoclonal antibody raised against the HA2 epitope;
NTA, nitrilotriacetic acid;
Mops, 3-(N-morpholino)propanesulfonic
acid.
 |
REFERENCES |
-
Nakamoto, R. K.
(1996)
J. Membr. Biol.
151,
101-111[CrossRef][Medline]
[Order article via Infotrieve]
-
Boyer, P. D.
(1997)
Annu. Rev. Biochem.
66,
717-749[CrossRef][Medline]
[Order article via Infotrieve]
-
Deckers-Hebestreit, G.,
and Altendorf, K.
(1996)
Annu. Rev. Microbiol.
50,
791-824[CrossRef][Medline]
[Order article via Infotrieve]
-
Jones, P. C.,
and Fillingame, R. H.
(1998)
J. Biol. Chem.
273,
29701-29705[Abstract/Free Full Text]
-
Abrahams, J. P.,
Leslie, A. G. W.,
Lutter, R.,
and Walker, J. E.
(1994)
Nature
370,
621-628[CrossRef][Medline]
[Order article via Infotrieve]
-
Noji, H.,
Yasuda, R.,
Yoshida, M.,
and Kinosita, K., Jr.
(1997)
Nature
386,
299-302[CrossRef][Medline]
[Order article via Infotrieve]
-
Kato-Yamada, Y.,
Noji, H.,
Yasuda, R.,
Kinosita, K., Jr.,
and Yoshida, M.
(1998)
J. Biol. Chem.
273,
19375-19377[Abstract/Free Full Text]
-
Junge, W.,
Lill, H.,
and Engelbrecht, S.
(1997)
Trends Biochem. Sci.
22,
420-423[CrossRef][Medline]
[Order article via Infotrieve]
-
Elston, T.,
Wang, H. Y.,
and Oster, G.
(1998)
Nature
391,
510-513[CrossRef][Medline]
[Order article via Infotrieve]
-
Dunn, S. D.
(1992)
J. Biol. Chem.
267,
7630-7636[Abstract/Free Full Text]
-
Girvin, M. E.,
Rastogi, V. K.,
Abildgaard, F.,
Markley, J. L.,
and Fillingame, R. H.
(1998)
Biochemistry
37,
8817-8824[CrossRef][Medline]
[Order article via Infotrieve]
-
Girvin, M. E.,
and Fillingame, R. H.
(1995)
Biochemistry
34,
1635-1645[Medline]
[Order article via Infotrieve]
-
Jones, P. C.,
Jiang, W.,
and Fillingame, R. H.
(1998)
J. Biol. Chem.
273,
17178-17185[Abstract/Free Full Text]
-
Jiang, W. P.,
and Fillingame, R. H.
(1998)
Proc. Natl. Acad. Sci. U. S. A
95,
6607-6612[Abstract/Free Full Text]
-
Valiyaveetil, F. I.,
and Fillingame, R. H.
(1997)
J. Biol. Chem.
272,
32635-32641[Abstract/Free Full Text]
-
Cain, B. D.,
and Simoni, R. D.
(1989)
J. Biol. Chem.
264,
3292-3300[Abstract/Free Full Text]
-
Lightowlers, R. N.,
Howitt, S. M.,
Hatch, L.,
Gibson, F.,
and Cox, G. B.
(1987)
Biochim. Biophys. Acta
894,
399-406[Medline]
[Order article via Infotrieve]
-
Long, J. C.,
Wang, S.,
and Vik, S. B.
(1998)
J. Biol. Chem.
273,
16235-16240[Abstract/Free Full Text]
-
Valiyaveetil, F. I.,
and Fillingame, R. H.
(1998)
J. Biol. Chem.
273,
16241-16247[Abstract/Free Full Text]
-
Jäger, H.,
Birkenhäger, R.,
Stalz, W. D.,
Altendorf, K.,
and Deckers-Hebestreit, G.
(1998)
Eur. J. Biochem.
251,
122-132[Abstract]
-
Yamada, H.,
Moriyama, Y.,
Maeda, M.,
and Futai, M.
(1996)
FEBS Lett.
390,
34-38[CrossRef][Medline]
[Order article via Infotrieve]
-
Vaara, M.
(1992)
Microbiol. Rev.
56,
395-411[Abstract]
-
Humbert, R.,
Brusilow, W. S.,
Gunsalus, R. P.,
Klionsky, D. J.,
and Simoni, R. D.
(1983)
J. Bacteriol.
153,
416-422[Medline]
[Order article via Infotrieve]
-
Hartzog, P. E.,
and Cain, B. D.
(1993)
J. Bacteriol.
175,
1337-1343[Abstract]
-
Vik, S. B.,
Cain, B. D.,
Chun, K. T.,
and Simoni, R. D.
(1988)
J. Biol. Chem.
263,
6599-6605[Abstract/Free Full Text]
-
Vik, S. B.,
Lee, D.,
and Marshall, P. A.
(1991)
J. Bacteriol.
173,
4544-4548[Medline]
[Order article via Infotrieve]
-
Matos, M.,
Fann, M. C.,
Yan, R. T.,
and Maloney, P. C.
(1996)
J. Biol. Chem.
271,
18571-18575[Abstract/Free Full Text]
-
Vik, S. B.,
Patterson, A. R.,
and Antonio, B. J.
(1998)
J. Biol. Chem.
273,
16229-16234[Abstract/Free Full Text]
Copyright © 1999 by The American Society for Biochemistry and Molecular Biology, Inc.