| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
ARTICLES |
Department of Molecular Biology and Pharmacology (T.H., D.M., I.B.), Washington University School of Medicine, St. Louis, Missouri 63110; Institute for Biomedical Aging Research (P.B.), Austrian Academy of Sciences, A-6020, Innsbruck, Austria
Address all correspondence and requests for reprints to: Irving Boime, Ph.D., Washington University Medical School, Department of Pharmacology, 660 South Euclid, St. Louis, Missouri 63110-1010. E-mail: iboime{at}pcg.wustl.edu
The crystal structure of human CG reveals that each subunit is a member
of the superfamily of cystine-knot growth factors. Although the
distribution of the cysteine residues in all the ß-subunits is
conserved, the conformation of the human FSH dimer differs from that of
the CG/LH dimers. This suggests that the function of the cystine bonded
loops in the human FSHß-subunit may differ from that in the
CGß-subunit. To address this issue, we deleted two disulfide bonds in
the FSHß domain: cys 20–104 and cys 28–82, which correspond to the
disulfide bonds 26–110 and 34–88, respectively, in the CGß-subunit.
The cys 26–110 bond is associated with the "seat-belt" region and
cys 34–88 is a bond in the cystine knot. Coexpression of the wild-type
-subunit with the FSHß cysteine mutants in CHO cells revealed no
detectable heterodimer. The FSHß mutants were then incorporated into
a single chain where the ß-subunit is genetically fused to the
-subunit. In such a model, the rate-limiting subunit assembly step
is by-passed and mutations that otherwise block heterodimer formation
can be evaluated in terms of biological activity. Compared with the
nonmutated single chain, the single-chain 28–82 mutant is secreted
more slowly and its recovery is substantially reduced, whereas
secretion and recovery of the 20–104 mutant was not significantly
affected. The receptor binding affinity of the cys 28–82 mutant did
not differ from wild-type and binding of the cys 20–104 mutant was
decreased only 2-fold. The signal transduction data parallel the
binding affinities, although the maximal accumulation of cAMP is less
for the cys 20–104 mutant than that seen for cys 28–82 and nonmutated
single-chains variants. These data support the hypothesis that the
determinants for intracellular behavior and bioactivity of the
gonadotropins are not the same, and that the cystine knot is a critical
determinant for the formation of a stable, assembly-competent subunit.
In addition, the data imply that the "seat-belt" conformation does
not play a prominent role in the bioactivity of FSH.
This article has been cited by other articles:
 |
|
 |
|
  A. Jablonka-Shariff, T. R. Kumar, J. Eklund, A. Comstock, and I. Boime Single-Chain, Triple-Domain Gonadotropin Analogs with Disulfide Bond Mutations in the {alpha}-Subunit Elicit Dual Follitropin and Lutropin Activities in Vivo Mol. Endocrinol., June 1, 2006; 20(6): 1437 - 1446. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 N. A. Horn, G. B. Hurst, A. Mayasundari, N. A. Whittemore, E. H. Serpersu, and C. B. Peterson Assignment of the Four Disulfides in the N-terminal Somatomedin B Domain of Native Vitronectin Isolated from Human Plasma J. Biol. Chem., August 20, 2004; 279(34): 35867 - 35878. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. B. Fralish, P. Narayan, and D. Puett Consequences of Single-Chain Translation on the Structures of Two Chorionic Gonadotropin Yoked Analogs in {alpha}-{beta} and {beta}-{alpha} Configurations Mol. Endocrinol., April 1, 2003; 17(4): 757 - 767. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. W. Szkudlinski, V. Fremont, C. Ronin, and B. D. Weintraub Thyroid-Stimulating Hormone and Thyroid-Stimulating Hormone Receptor Structure-Function Relationships Physiol Rev, April 1, 2002; 82(2): 473 - 502. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Endocrinology | Endocrine Reviews | J. Clin. End. & Metab. |
| Molecular Endocrinology | Recent Prog. Horm. Res. | All Endocrine Journals |
