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Medical AI Inquiry: You was designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.  Labels: OBJECTIVE, METHODS, METHODS, RESULTS. Meshes: Amino Acid Sequence, Animals, COS Cells, Cell Membrane, Chorionic Gonadotropin, Codon, Humans, Leydig Cells, Luteinizing Hormone, Male, Mutation, Rats, Receptors, LH, Recombinant Proteins, Swine, Testis, Testosterone.
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Does human chorionic gonadotropin with C-elongated alpha-subunit retain full receptor binding and partial agonist activity? Context: To test whether extension of the C-terminus of human chorionic gonadotropin (hCG) alpha-subunit (halpha) alters the bioactivity of the recombined alphabeta heterodimer. The stop codon of halpha was mutated to produce a 24 amino acid extension. The extended halpha (alpha(+24)) was co-expressed with hCGbeta in COS-7 cells and the receptor binding and in vivo bioactivity of the secreted hormone was compared with its wild-type counterpart. This extension did not impair the binding of hCG to rat LH/CG receptors and provoked a sixfold reduction in its stimulatory activity of testosterone secretion in rat Leydig cells.
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The extension of alpha by itself does not lead to inhibition of the alphabeta heterodimer to LH receptors but the structure of the extension appears to play an important role. It is thus possible that one-chain hCG chimeras with the beta N-terminus fused to the alpha C-terminus might be active. Final Decision: yes