Generation of two water-soluble components from particulate receptor-human chorionic gonadotropin complex by endogenous proteolysis of the receptor.
Rat ovarian and testicular particles prelabelled with human [125I]CG (ovary) or [131I]CG (testis) were incubated in low ionic strength medium and the water-soluble components obtained from the particulate receptor-human CG complexes were characterized and compared. Sedimentation coefficients determined by sucrose density gradient centrifugation were 4.3 S for the ovarian and 4.9 S for the testicular component run in the same sample. Gel filtration analyses displayed, however, that both from the ovarian and testicular particles two components of different sizes were released, the smaller form (hydrodynamic radius of 3.9 nm) being dominant for the ovary, and the larger one (hydrodynamic radius of 4.8 nm) dominant for the testis. The molecular weights determined by SDS-polyacrylamide gel electrophoresis were 100 000 and 72 000 for the testicular, and 94 000 and 72 000 for the ovarian components. Analyses of the ovarian components by gel filtration, ion exchange chromatography and reversed-phase HPLC technique showed further that these components differ also from each other in their charge and solubility to organic solvents, and that both of them contain intact human CG as a part of their structure. These results demonstrate that two water-soluble components are released from rat testis and ovary, both of which are distinctly smaller in size than detergent-solubilized receptor-human CG complexes. Our interpretation is that they are formed by endogenous proteolysis of the receptor, at two distinct sites, respectively.
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D006063:Chorionic Gonadotropin / Q000378:metabolism*; D005260:Female; D008297:Male; D010053:Ovary / Q000378:metabolism*; D010446:Peptide Fragments / Q000032:analysis; D051381:Rats; D011919:Rats, Inbred Strains; D011956:Receptors, Cell Surface / Q000302:isolation & purification / Q000378:metabolism*; D011974:Receptors, LH; D012995:Solubility; D013737:Testis / Q000378:metabolism*
D006063:Chorionic Gonadotropin; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D011974:Receptors, LH