Follicle stimulating hormone (FSH) induces G protein dissociation from FSH receptor-G protein complexes in reconstituted proteoliposomes.
We have previously reported incorporation of Triton X-100-solubilized bovine calf testis membrane protein into liposomes. The resulting proteoliposomes responded to FSH by exchange of bound GDP for [3H]5'-guanylyl imidodiphosphate ([3H]Gpp(NH)p) and by activation of adenylate cyclase (AC) (Grasso, P., Dattatreyamurty, B. and Reichert, L.E., Jr. (1988) Mol. Endocrinol. 2, 420-430). This model system was utilized to study the effects of FSH on the quaternary structure of FSH receptor-associated GTP-binding protein by comparing the gel filtration profiles of proteoliposomes solubilized with Triton X-100 after exposure to [3H]Gpp(NH)p in the presence or absence of FSH. FSH caused a redistribution of radioactivity (due to bound [3H]Gpp(NH)p) from a high molecular weight fraction (Mr greater than 100,000) to a fraction of much lower molecular weight (Mr approximately 23,000). These results are interpreted to reflect an FSH-induced dissociation of [3H]Gpp(NH)p-bound G protein from its receptor-associated complex. The apparent Mr of approximately 23,000 for the FSH receptor-associated GTP-binding protein suggests that it may represent yet another member of a family of low molecular weight GTP-binding proteins, possibly a ras gene product, recently identified in various mammalian tissues.
Grasso
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Department of Biochemistry, Albany Medical College, New York 12208.
Reichert
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D000818:Animals; D002417:Cattle; D002850:Chromatography, Gel; D005640:Follicle Stimulating Hormone / Q000494:pharmacology*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D006165:Guanylyl Imidodiphosphate / Q000378:metabolism; D066298:In Vitro Techniques; D008081:Liposomes; D046911:Macromolecular Substances; D008274:Magnesium / Q000494:pharmacology; D008970:Molecular Weight; D011485:Protein Binding; D011962:Receptors, FSH / Q000378:metabolism*
D008081:Liposomes; D046911:Macromolecular Substances; D011962:Receptors, FSH; D006165:Guanylyl Imidodiphosphate; D005640:Follicle Stimulating Hormone; D019204:GTP-Binding Proteins; D008274:Magnesium