Hormone Interactions to Leu-rich Repeats in the Gonadotropin
Receptors
II. ANALYSIS OF LEU-RICH REPEAT 4 OF HUMAN LUTEINIZING
HORMONE/CHORIONIC GONADOTROPIN RECEPTOR*
Yong Sang
Song
§,
Inhae
Ji
,
Jeremy
Beauchamp¶,
Neil W.
Isaacs¶, and
Tae H.
Ji
From the
Department of Chemistry, University of
Kentucky, Lexington, Kentucky 40506-0055, the § Cancer
Research Center, Seoul National University College of Medicine, Seoul
110-744, Korea, and the ¶ Department of Chemistry, University
of Glasgow, Glasgow G128QQ, United Kingdom
Received for publication, May 3, 2000, and in revised form, July 5, 2000
 |
ABSTRACT |
The luteinizing hormone receptor (LHR) consists
of an ~350-amino acid-long N-terminal extracellular exodomain and a
membrane-associated endodomain of similar size. Human chorionic
gonadotropin (hCG) binds to the exodomain, and then hCG/exodomain
complex is thought to make a secondary contact with the endodomain and
generate hormone signals. The sequence alignment of the exodomain shows
imperfectly matching eight to nine Leu-rich repeats (LRRs). In the
preceding article (Song, Y., Ji, I., Beauchamp, J., Isaacs, N., and Ji, T. (2001) J. Biol. Chem. 276, 3426-3435), we
have shown that LRR2 and LRR4 are crucial for hormone binding. In this
work, we have examined the residues of LRR4, in particular
Leu103 and Ile105 in the putative
strand.
Our data show that Leu103 and Ile105 are
involved in the specific, hydrophobic interaction of the LRR4 loop,
likely to form the hydrophobic core. This loop is crucial for the
structural integrity of all of the LRRs. In contrast, the downstream
sequence consisting of Asn107, Thr108,
Gly109, and Ile110 of LRR4 is crucial for cAMP
induction but not for hormone binding, folding, and surface expression.
This implicates, for the first time, its involvement in the interaction
with the endodomain and signal generation. The evidence for the
interaction is presented in the following article.
 |
INTRODUCTION |
The luteinizing hormone/chorionic gonadotropin receptor
(LHR)1 plays crucial roles in
development of the gonads in both sexes and the ovulation cycle of the
females (1, 2). LHR is a member of the glycoprotein hormone receptor
subfamily, which includes the follicle-stimulating hormone receptor and
the thyroid-stimulating hormone receptor in the G protein-coupled
receptor superfamily. It consists of an extracellular N-terminal half
(exodomain) and a membrane-associated C-terminal half (endodomain) (3,
4). The ~350-amino acid-long exodomain is responsible for high
affinity hormone binding (5-7) and hormone specificity (8-10). The
resulting hCG-exodomain complex is thought to make a secondary
contact with the endodomain, which generates hormone signal (11-13).
Despite the importance of this secondary contact, it has been difficult to find any clues for the secondary contact points. These contact points and residues are likely to be the site of signal generation and
play a key role in the signal generation.
The exodomain contains imperfect Leu/Ile-rich repeats (LRRs) of 22-29
amino acids (3, 14-18), which are a common structural motif found in a
large family of proteins, including glycoprotein hormone receptors
(19). In the crystals of ribonuclease inhibitors, individual LRRs
consist of a
strand connected to a parallel
helices despite
divergent sequences. In each
strand, there are two conserved Leu
and/or Ile residues in the alternate positions as
Leu/Ile-X-Leu/Ile. Therefore, the primary homology among
LRRs is the Leu/Ile-X-Leu/Ile motif in
strands.
Furthermore, the
strands in ribonuclease inhibitors are involved in
the interaction with ribonuclease. However, it has been unknown whether
the putative LRRs of the LHR are active at all and what their nature
and function are. In the preceding article (20) we have shown that
some, but not all, LRRs of the LHR and the FSH-R are crucial for
hormone binding. In LHR, LRR2 and LRR4 are crucial.
In this study, the residues around the Leu-Ser-Ile motif in LRR4 of LHR
were examined. Our results suggest that the Leu and Ile are involved in
the specific and tightly packed hydrophobic interaction in the core of
LRR4 loop. In addition, our data implicate, for the first time, the
involvement of LRR4 in the interaction of the hCG-exodomain complex
with the endodomain. The evidence is presented in the following
companion article (21).
 |
EXPERIMENTAL PROCEDURES |
Mutant human LHR cDNAs were prepared, expressed in HEK 293 cells, and assayed for hormone binding and intracellular cAMP
production as described previously (20, 22). All assays were carried out in duplicate and repeated four to six times. Means and standard variations were calculated. FLAG-LHR was prepared by inserting the FLAG epitope (23), Asp-Tyr-Lys-Asp-Asp-Asp-Asp-Lys, between the C
terminus (Ser26) of the signal sequence and the N terminus
(Arg27) of mature receptors. (20).
 |
RESULTS |
To investigate the Leu-Ser-Ile motif of LRR4 in LHR, we decided to
examine the extended sequence encompassing the motif and the flanking
residues,
Arg99-Leu-Lys-Tyr-Leu-Ser-Ile-Cys-Asn-Thr-Gly-Ile-Arg-Lys112.
These residues were individually substituted with Ala, and each of the
Ala substitution mutants was stably expressed in HEK 293 cells.
They were assayed for 125I-hCG binding on intact cells or
after solubilization in Triton X-100 and for hCG-dependent
cAMP induction. As shown by the binding displacement data and Scatchard
plots in Fig. 1, the cells transfected with the vector carrying the Arg99
Ala mutant bound
125I-hCG with a Kd value of 1,410 pM as intact cells (Fig. 1, A and B)
or 1,640 pM after solubilization (Fig. 1, C and
D). These values were higher than the corresponding wild
type values of 600 pM and 1,100 pM. In
contrast, the cells that were transfected with the vector containing no
receptor cDNA or were not transfected at all did not bind the
hormone (data not included). These results indicate that the cells
transfected with the Arg99
Ala plasmid expressed the
mutant receptor on the cell surface as well as in the cells and that
the mutant was capable of binding hCG. In addition, the cells produced
cAMP in response to hCG in a dose-dependent manner with an
EC50 value of 230 pM and a maximum cAMP level
of 72 fmol/1,000 cells. The EC50 value of cAMP induction, 230 pM, is 39% of the wild type value of 89 pM. Therefore, the higher Kd value
resulted in the higher EC50 value. However, the inverse was
not observed. For example, a higher binding affinity does not
necessarily correlates with lower EC50 for cAMP induction. Furthermore, maximum cAMP production does not consistently
correlates with an EC50 value. Taken together, the
affinities of hormone binding and cAMP induction of the
Arg99
Ala mutant are consistently less than one-half of
the corresponding wild type affinities. Consequently, the lower
affinity and efficacy to induce cAMP is likely due to the lower hormone
binding affinity rather than to a defective intrinsic mechanism in cAMP
induction. However, this correlation is limited, because the opposite
is not true.

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Fig. 1.
Ala scan and characterization of residues
around the conserved Leu103/Ile105 motif in
LRR4 of LHR. Amino acids from Arg99 to
Lys112 encompassing the conserved
Leu103/Ile105 motif in the putative strand
of LRR4 were individually substituted with Ala. The resulting mutant
receptors were stably expressed on human 293 cells. Cells were assayed
for 125I-hCG binding in the presence of increasing
concentrations of nonradioactive hCG (A), and Scatchard
analysis (B) was plotted against specific binding. Cells
were also solubilized in Triton X-100 and assayed for
125I-hCG binding in the presence of unlabeled hCG
(C), and the results were converted to Scatchard plots
(D). In addition, intact cells were treated with increasing
concentrations of unlabeled hCG and intracellular cAMP was measured
(E) as described under "Experimental Procedures."
Experiments were repeated four to six times in duplicate. NS stands for
not significant.
|
|
In contrast to the hormone-responsive Arg99
Ala mutant,
the Leu100
Ala did not show hCG binding to intact cells
(Fig. 1). To test whether the Leu100
Ala mutant was
capable of binding hCG but trapped in cells, the cells transfected with
the Leu100
Ala mutant vector were solubilized in Triton
X-100 and assayed for 125I-hCG binding (Fig. 1,
C and D). Again, 125I-hCG binding was
not observed. In addition, the cells did not respond to hCG to produce
cAMP (Fig. 1E). These results are generally considered as
evidence for a receptor defective in hormone binding (18, 20, 24, 25).
To demonstrate their expression on the cell surface, the mutant
receptor containing the FLAG tag and monoclonal anti-FLAG antibody was
used. The antibody recognized the intact cells expressing the
FLAG-Leu100
Ala mutant (35 ± 9% of the wild type
expression), indicating the surface expression of the
FLAG-Leu100
Ala mutant (20).
Next, the Lys101
Ala mutant was examined.
125I-hCG bound to intact cells expressing the
Lys101
Ala mutant with a Kd value of
1,640 pM and cells solubilized in Triton X-100 with a
Kd value of 1,860 pM (Fig. 1). cAMP was
produced in response to hCG with an EC50 of 214 pM and a maximum cAMP level of 68 fmol/1,000 cells. These
results are similar to those of the Arg99
Ala mutant,
indicating that the Arg99
Ala and Lys101
Ala mutants behaved the same and the Ala substitution for
Arg99 and Lys101 had the similar effect. The
effect of the Ala substitution for the next residue,
Tyr102, was more severe, although it did not abolish the
activity of the mutant (Fig. 1). For example, the Kd
values for binding to intact cells and solubilized cells were 4,610 and
7,800 pM, respectively, while the EC50 for cAMP
production was 720 pM. These affinities of the mutant are
only 12-14% of the wild type values, although the maximum cAMP level
was 120 fmol/1,000 cells, which is nearly 80% of the wild type level
(Table I).
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Table I
Percent Kd, EC50, and maximum cAMP values of Ala
substitution mutants
Kdwt/mut values for Ala substitution mutants
in Fig. 1 were calculated by dividing the wild type
Kd with the mutant Kd values as
were EC50 values. Maximum cAMP values were calculated by
dividing maximum cAMP of each mutant with that of the wild type
receptor. NS stands for "not significant." In addition, ratios of
(EC50wt/mut)/(Kdwt/mut) and
(maxmut/wt)/(Kdwt/mut) are
presented.
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The effects of the Ala substitution for the next three residues
were similar to or more severe than the effect of the
Tyr102
Ala substitution. For example, the
Ser104
Ala mutant had Kd values of
3,600 and 5,370 pM for hormone binding to intact cells and
solubilized cells, respectively (Fig. 1, F-I). The
EC50 value for cAMP induction was 599 pM (Fig. 1J). The affinities for hormone binding to intact cells and
cAMP induction were, therefore, only 15-17% of the wild type
affinities (Table I). Leu103
Ala and Ile105
Ala resulted in the complete loss of hormone binding both to intact
cells and solubilized cells as well as hCG-dependent cAMP induction (Fig. 1, F-J). These two residues correspond to
the conserved Leu/Ile-X-Leu/Ile motif in the
strands of
LRRs. Ala substitutions for Cys106, Asn107,
Thr108, Gly109, Ile110,
Arg111, and Lys112 did not abolish hormone
binding but attenuated the binding affinity (Fig. 1, F-O,
and Table I). All of the mutant receptors were also capable of inducing
cAMP synthesis. These results indicate that the conserved
Leu/Ile-X-Leu/Ile motif, Leu103 and
Ile105, is indeed more sensitive to Ala substitution than
the flanking residues except Leu100. Interestingly, this
was independent of the chemical and physical properties of the side
chains of the flanking residues.
Since these results are consistent with the LRR hypothesis, we
investigated the nature of the Leu103
Ala and
Ile105
Ala substitutions by replacing
Leu103 and Ile105 with a panel of amino acids
containing hydrophobic, hydrophilic, neutral, anionic, and cationic
side chains. First, Leu103 was substituted with various
hydrophobic amino acids. The substitutions of Val, Phe, and Ile
increased the Kd values up to 10-fold (Fig.
2, A-D), thus reducing the
affinity to 11-44% of the wild type (Table
II), but did not abrogate hormone binding
and cAMP induction (Fig. 2E). It is notable that the
Leu103
Ile mutant was the one with the binding affinity
of only 10% of the wild type. This suggests that Ile could not replace
Leu103 without impacting the receptor function. When
Leu103 was substituted with Trp, the bulkiest hydrophobic
amino acid, the mutant did not show hormone binding to intact cells and
solubilized receptors. Similarly, the mutant receptor with the
substitution of hydrophilic Thr, neutral Asn, anionic Asp, or cationic
Lys did not bind the hormone (Fig. 2, F-H). Since these
substitutions introduced an amino acid with a different side chain, it
is difficult to tell whether the substitution effects were due to the
missing side chain of Leu or the newly introduced side chain. To test these possibilities, Leu103 was deleted, and the resulting
Leu103
deletion mutant did not bind the hormone
(Fig. 2, F-H).

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Fig. 2.
Multiple substitutions for
Leu103. Leu103 was substituted with a
panel of amino acids with hydrophobic, hydrophilic, neutral, anionic,
and cationic side chains. In addition, Leu103 was deleted
in a mutant. The resulting mutant receptors were stably expressed on
human 293 cells. Cells were assayed for 125I-hCG binding
and hCG-dependent cAMP induction as described in the legend
to Fig. 1.
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Table II
Kd, EC50, and maximum cAMP values of
substitution mutants of Leu103 and Ile105
Kdwt/Kdmut for
Ala substitution mutants in Figs. 2 and 3 were calculated as described
in Table I.
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Next, Ile105 was examined after substitutions. The
substitutions of Phe, Val, and Leu were tolerable, as the resulting
mutants were capable of hormone binding and inducing cAMP (Fig.
3, A-E), although the
affinities were reduced to 16-56% of the wild type affinity (Table
II). This is similar to the Phe, Val, and Ile substitutions for
Leu103. Interestingly, the Val substitution impacted the
least for both Leu103, whereas the Phe substitution did the
least for Ile105, suggesting the distinct environment of
the two residues. On the other hand, the Trp substitution resulted in
the complete loss of the activity for both of Ile105 and
Ile103. The substitution for Ile105 with
nonhydrophobic Thr, Asn, Asp, or Lys completely impaired the receptor
activity as was the case with Leu103 (Fig. 3,
F-H). To investigate the relationship between
Leu103 and Ile105, a reciprocal mutant with
Leu103
Ile and Ile105
Leu was
generated. The resulting double mutant. Leu103
Ile/Ile105
Leu, poorly bound the hormone with a
Kd value of 3,340 pM on intact cells and
with a Kd value of 6,970 pM in solution
(Fig. 4). These values indicate that the
binding affinities are <20% of the corresponding wild type
affinities, consistent with the view of the distinct environment of
Leu103 and Ile105.

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Fig. 3.
Multiple substitutions for
Ile105. Ile105 was substituted with a
panel of amino acids with hydrophobic, hydrophilic, neutral, anionic,
and cationic side chains. In addition, Ile105 was deleted
in a mutant. The resulting mutant receptors were stably expressed on
HEK 293 cells. Cells were assayed for 125I-hCG
binding and hCG-dependent cAMP induction as described in
the legend to Fig. 1.
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Fig. 4.
Reciprocal double substitutions for
Leu103 and Ile105. Leu103 and
Ile105 were substituted with a Ile and Leu, respectively,
and the resulting mutant receptor was stably expressed on HEK
293 cells. Cells were assayed for 125I-hCG binding and
hCG-dependent cAMP induction as described in the legend to
Fig. 1.
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To determine whether the double mutant receptor was expressed at all,
the FLAG-Leu103
Ile/Ile105
Leu receptor
was tested. 125I-Monoclonal anti-FLAG antibody bound to the
intact cells as well as solubilized cells that were transfected with
the FLAG-Leu103
Ile/Ile105
Leu plasmid
(data not included). In contrast, cells that were not transfected or
transfected with the LHR with Leu103
Ile/Ile105
Leu plasmid did not bind the antibody. These
results clearly indicate expression of FLAG-LHR with Leu103
Ile/Ile105
Leu on the cell surface and in cells, as
well as expression of the Leu103
Ile/Ile105
Leu mutant lacking the FLAG epitope. When the Leu103
Ile/Ile105
Leu mutant was reverted to the wild type
receptor, the revertant was capable of binding the hormone and inducing
cAMP production. Therefore, the inability of the Leu103
Ile/Ile105
Leu mutant to bind the hormone and induce
cAMP was due to the double substitutions, not due to unexpected random
mutations during the mutagenesis and cloning.
 |
DISCUSSION |
The results observed in this work show that the Ala substitutions
for Leu103 and Ile105 abolished the hormone
binding activity of the receptor, whereas the Ala substitution for
Tyr102 and Ser104 severely impaired the
receptor. In contrast to these four crucial and tandem residues, other
residues among the sequence of the 14 amino acids,
Arg99-Leu-Lys-Tyr-Leu-Ser-Ile-Cys-Asn-Thr-Gly-Ile-Arg-Lys112,
in the putative LRR4 are marginally or less severely impacted by Ala
substitution except Leu100. Therefore, the sequence of
Tyr102-Leu103-Ser104-Ile105
appears to be crucial for hormone binding and may constitute the core
of the putative
strand of LRR4. This
configuration would orient Leu103 and
Ile105 at one side and Tyr102 and
Ser104 at the other side of the
strand, suggesting a
hydrophobic core comprising Leu103 and Ile105
and a hydrophilic phase with Tyr102 and Ser104.
The hydrophobic core may include Leu100, as it is equally
sensitive to Ala substitution. In fact, the result of multiple
substitutions for Leu103-Ile105 indicate such
a hydrophobic core, since only hydrophobic residues larger than Ala,
but less bulky than Trp, are tolerable at the positions of
Leu103 and Ile105. Substitutions with
hydrophilic, neutral, cationic, and anionic residues totally impaired
the receptor activity. These results suggest that the hydrophobic core
is compact and specific.
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Table III
Comparison of the LRR4 sequence
The sequences encompassing the Leu-X-Ile in the strand
of LRR4 of glycoprotein hormone receptors were aligned. Absolutely
conserved residues are marked with "*".
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It is interesting to note that the hormone binding affinity of the
reciprocal double mutant, Leu103
Ile/Ile105
Leu was similar to the binding affinity of the single substitution mutant with Leu103
Ile or Ile105
Leu.
These results indicate that Leu103 and Ile105
in the putative LRR4
strand could not be switched with each other,
consistent with the compact and specific nature of the hydrophobic
core. Furthermore, they suggest that the substitutions do not have a
synergistic effect. A simple explanation in this particular case is
that Leu103 or Ile105 may interact with each
other as well as other residues. As a result, the interruption of
either or both of them would have the similar effect. This hypothesis
is consistent with the remarkably similar trends of substitutions for
Leu103 and Ile105. For example, the
substitutions of Val and Phe were tolerable to both Leu103
and Ile105, whereas the substitutions of Ala, Trp, Thr,
Asn, Asp, and Lys abolished the receptor activity. The Val substitution
was most tolerable for Leu103 with a Kd
value of 1,410 pM, whereas the Phe substitution for
Leu103 is less tolerable with a Kd value
of 3,730 pM. The trend was opposite for Ile105.
The Phe substitution was most tolerable with a Kd
value of 1,110 pM, whereas the Val substitution is less
tolerable with a Kd value of 3,820 pM.
The common and specific nature of their hydrophobic environment is
consistent with our model (Fig. 5),
showing the direct interaction of Leu103 with
Ile105 and Leu100 in a hydrophobic pocket of
LRR4.

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Fig. 5.
Computer modeling of LRR4. The
data presented in Figs. 1 and 2 suggested a hydrophobic core of LRR4.
Based on these results, LRR4 was modeled to form a hydrophobic core
(20), similar to the hydrophobic cores of the Leu-rich repeats found in
the crystal structure of ribonuclease inhibitors (19). Once the
hydrophobic core is factored in with the side chains of
Leu100, Leu103, Ile105, and
Ile110, the orientation of the side chains of other
residues are determined by energy minimization. Yellow
indicates an natural residue, red indicates Ala
substitutions with a maximum effect on hormone binding
(Kd of hormone binding to cells) and/or expression,
and blue indicates a minimum effect on hormone binding.
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Our studies have been focused on the two primary targets, the
interaction between the exodomain and hormone (initial high affinity
binding) and the interaction between the hCG-exodomain complex and the
endodomain (signal generation). It has been very difficult to find any
clues for the contact site(s) of the exodomain for the endodomain. Our
data presented in Figs. 1 and 2 as well as Table I are the first to
implicate the involvement of LRR4 in contacting the endodomain, in
particular, Gly109. The reason is as follows: most of Ala
substitutions for LRR4 residues reduced the maximum cAMP induction up
to 41% of the wild type value. The only exception is
Gly109
Ala substitution, which nearly abolished cAMP
induction to 14% of the wild type value. This trend is more obvious
when the (maximum
cAMPmut/wt)/(Kdwt/mut, where
mut indicates mutant and wt indicates wild type) ratios are compared
among the Ala mutants (Table I). The ratios are more than 1.00 for all
except Gly109
Ala and Asn107
Ala. The
ratios for the two mutants are 0.52 and 0.71, and such exceptionally
low ratios are not found with any LRR2 Ala mutants (20). The sequence
alignment reveals the striking conservation of the amino acids from
Leu97-Pro-Gly-Leu-Lys-Tyr-Leu-Ser-Ile-Cys-Asn-Thr-Gly109
(Table III). Out of the 13 amino acids, 8 are absolutely
identical among LHR, follicle-stimulating hormone receptor, and
thyroid-stimulating hormone receptor of all species. Interestingly,
Asn107-Thr-Gly109 are uniquely in tandem
and their maximum
cAMPmut/wt)/(Kdwt/mut)
ratios are 0.71, 1.08, and 0.52, respectively. These residues are not
essential for folding and surface expression, since the Ala mutants
were successfully expressed on the cell surface and capable of binding
the hormone. However, Ala substitution of them notably impaired cAMP
induction as obvious by their significantly high
EC50 for cAMP and/or low maximum cAMP level (Table
I), suggesting an intriguing possibility of their interaction with the endodomain.
In conclusion, the Leu103-Ile105 sequence is
crucial for the specific interaction to form the hydrophobic core of
LRR4. In addition, the downstream sequence consisting of
Asn107, Thr108, and Gly109 is
crucial for cAMP induction but not for hormone binding, folding, and
surface expression. Therefore, they are likely involved in the
interaction with the endodomain. This is the first evidence suggesting
an endodomain contact point in the exodomain. Then, the inevitable
question is whether LRR4 interacts with hCG at all. In the following
article (21) we show evidence that LRR4 does interact with hCG and,
furthermore, is involved in the interaction of hCG-exodomain complex
with the endodomain.
 |
FOOTNOTES |
*
This work was supported by Grants HD-18702 and DK-51469 from
the National Institutes of Health.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 all correspondence should be addressed: Dept. of
Chemistry, University of Kentucky, Lexington, KY 40506-0055. Tel.: 859-257-3163; Fax 859-527-3229; E-mail: tji@pop.uky.edu.
Published, JBC Papers in Press, July 6, 2000, DOI 10.1074/jbc.M003773200
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ABBREVIATIONS |
The abbreviations used are:
LH, luteinizing
hormone;
LHR, LH receptor;
CG, choriogonadotropin;
h, human;
LRR, Leu-rich repeat;
HEK, human embryonic kidney;
mut, mutant;
wt, wild
type.
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REFERENCES |
1.
|
Hsueh, A. J.,
Jones, P. B.,
Adashi, E. Y.,
Wang, C.,
Zhuang, L. Z.,
and Welsh, T. H., Jr.
(1983)
J. Reprod. Fertil.
69,
325-342[Abstract]
|
2.
|
Griswold, M. D.
(1993)
in
The Sertoli Cells
(Russell, L. D.
, and Griswold, M. D., eds)
, pp. 496-508, Cache River Press, Clearwater, FL
|
3.
|
McFarland, K.,
Sprengel, R.,
Phillips, H.,
Kohler, M.,
Rosemblit, N.,
Nikolics, K.,
Segaloff, D.,
and Seeburg, P.
(1989)
Science
245,
494-499[Medline]
[Order article via Infotrieve]
|
4.
|
Loosfelt, H.,
Misrahi, M.,
Atger, M.,
Salesse, R.,
Thi, M.,
Jolivet, A.,
Guiochon-Mantel, A.,
Sar, S.,
Jallal, B.,
Garnier, J.,
and Milgrom, E.
(1989)
Science
245,
525-528[Medline]
[Order article via Infotrieve]
|
5.
|
Tsai-Morris, C. H.,
Buczko, E.,
Wang, W.,
and Dufau, M. L.
(1990)
J. Biol. Chem.
265,
19385-19388[Abstract/Free Full Text]
|
6.
|
Xie, Y. B.,
Wang, H.,
and Segaloff, D. L.
(1990)
J. Biol. Chem.
265,
21411-21414[Abstract/Free Full Text]
|
7.
|
Ji, I.,
and Ji, T. H.
(1991)
Endocrinology
128,
2648-2650[Abstract]
|
8.
|
Braun, T.,
Schofield, P. R.,
and Sprengel, R.
(1991)
EMBO J.
10,
1885-1890[Abstract]
|
9.
|
Moyle, W. R.,
Campbell, R. K.,
Myers, R. V.,
Bernard, M. P.,
Han, Y.,
and Wang, X.
(1994)
Nature
368,
251-255[CrossRef][Medline]
[Order article via Infotrieve]
|
10.
|
Liu, X.,
DePasquale, J. A.,
Griswold, M. D.,
and Dias, J. A.
(1994)
Endocrinology
135,
682-691[Abstract]
|
11.
|
Ji, T. H.,
Murdoch, W. J.,
and Ji, I.
(1995)
Endocrine
3,
187-194
|
12.
|
Dufau, M. L.
(1998)
Annu. Rev. Physiol.
60,
461-496[CrossRef][Medline]
[Order article via Infotrieve]
|
13.
|
Ji, T. H.,
Grossmann, M.,
and Ji, I.
(1998)
J. Biol. Chem.
273,
17299-17302[Free Full Text]
|
14.
|
Koo, Y. B.,
Ji, I.,
Slaughter, R. G.,
and Ji, T. H.
(1991)
Endocrinology
128,
2297-2308[Abstract]
|
15.
|
Moyle, W.,
Campbell, R.,
Rao, S.,
Ayad, N.,
Bernard, M.,
Han, Y.,
and Wang, Y.
(1995)
J. Biol. Chem.
270,
20020-20031[Abstract/Free Full Text]
|
16.
|
Jiang, X.,
Dreno, M.,
Buckler, D.,
Cheng, S.,
Ythier, A.,
Wu, H.,
Hendrickson, W.,
and Tayar, N.
(1995)
Structure (Lond.)
3,
1341-1353[Medline]
[Order article via Infotrieve]
|
17.
|
Couture, L.,
Naharisoa, H.,
Grebert, D.,
Remy, J. J.,
Pajot-Augy, E.,
Bozon, V.,
Haertle, T.,
and Salesse, R.
(1996)
J. Mol. Endocrinol.
16,
15-25[Abstract]
|
18.
|
Bhowmick, N.,
Huang, J.,
Puett, D.,
Isaacs, N. W.,
and Lapthorn, A. J.
(1996)
Mol. Endocrinol.
10,
1147-1159[Abstract]
|
19.
|
Kobe, B.,
and Deisenhofer, J.
(1994)
Trends Biochem. Sci.
19,
415-421[CrossRef][Medline]
[Order article via Infotrieve]
|
20.
|
Song, Y.,
Ji, I.,
Beauchamp, J.,
Isaacs, N.,
and Ji, T.
(2001)
J. Biol. Chem.
276,
3426-3435[Abstract/Free Full Text]
|
21.
|
Jeoung, M.,
Phang, T.,
Song, Y.,
Ji, I.,
and Ji, T.
(2001)
J. Biol. Chem.
276,
3443-3450[Abstract/Free Full Text]
|
22.
|
Ji, I.,
and Ji, T. H.
(1995)
J. Biol. Chem.
270,
15970-15973[Abstract/Free Full Text]
|
23.
|
Prikett, K.,
Amberg, D.,
and Hopp, T.
(1989)
BioTechniques
7,
580-589[Medline]
[Order article via Infotrieve]
|
24.
|
Abell, A.,
Liu, X.,
and Segaloff, D. L.
(1996)
J. Biol. Chem.
271,
4518-4527[Abstract/Free Full Text]
|
25.
|
Hong, S.,
Phang, T.,
Ji, I.,
and Ji, T. H.
(1998)
J. Biol. Chem.
273,
13835-13840[Abstract/Free Full Text]
|
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