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Functional homodimeric glycoprotein hormones: implications for hormone action and evolution.
- Source :
-
Chemistry & biology [Chem Biol] 1998 May; Vol. 5 (5), pp. 241-54. - Publication Year :
- 1998
-
Abstract
- Background: Human chorionic gonadotropin (hCG), lutropin, follitropin, and thyrotropin act as alpha beta heterodimers to control reproduction and thyroid function. The alpha and beta subunits of these proteins are divided into three loops (alpha 1,alpha 2,alpha 3; beta 1,beta 2,beta 3) by cysteine knots and the heterodimer is stabilized by 20 beta-subunit residues wrapped around alpha 2 like a seatbelt. Understanding how these hormones interact with their receptors, a matter of considerable dispute, would facilitate design of pro- and anti-fertility agents.<br />Results: By swapping alpha 2 for beta 2 and vice versa and, in some cases, adding an amino-terminal coiled-coil dimerization domain, we prepared homodimeric analogs that have the conformation found in each 'half' of hCG. Homodimers containing loops beta 1,alpha 2,beta 3 and none, part, or all of the seatbelt stimulated signal transduction to the same extent as hCG, albeit with lower potency. Those containing alpha 1,beta 2,alpha 3 were inactive.<br />Conclusions: The activities of homodimers containing the beta 1,alpha 2,beta 3 groove exceed those of other minimized analogs more than 100-1000-fold, suggesting this portion of the hormone forms the major receptor contact. The discovery that glycoprotein hormone heterodimers can be converted to functional homodimers supports the proposal that this protein family evolved from an active homodimeric ancestor by gene duplication and acquisition of mutations to loop 2 that prevent homodimerization. This approach to protein minimization should be applicable to other proteins composed of architecturally related subunits, including those that might have arisen by gene duplication.
- Subjects :
- Amino Acid Sequence
Animals
Chorionic Gonadotropin chemistry
Chorionic Gonadotropin genetics
Dimerization
Follicle Stimulating Hormone chemistry
Follicle Stimulating Hormone genetics
Humans
Luteinizing Hormone chemistry
Luteinizing Hormone genetics
Molecular Sequence Data
Protein Conformation
Receptors, Cell Surface physiology
Reproduction physiology
Sequence Homology, Amino Acid
Thyrotropin chemistry
Thyrotropin genetics
Chorionic Gonadotropin physiology
Evolution, Molecular
Follicle Stimulating Hormone physiology
Luteinizing Hormone physiology
Thyrotropin physiology
Subjects
Details
- Language :
- English
- ISSN :
- 1074-5521
- Volume :
- 5
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Chemistry & biology
- Publication Type :
- Academic Journal
- Accession number :
- 9646940