title: Biological activity of single chain chorionic gonadotropin, hCGalphabeta, is decreased upon deletion of five carboxyl terminal amino acids of the alpha subunit without affecting its receptor binding.
abstract: The strategy of translationally fusing the two subunits of human chorionic gonadotropin (hCG) has been used to produce recombinant single chain hCG in which the C-terminus of the alpha subunit is fused to the N-terminus beta without any linker using Pichia pastoris expression system. The Pichia-expressed hCGalphabeta (phCGalphabeta) attained an overall conformation similar to that of hCG, and could bind to the receptor and elicit biological response, suggesting that receptor binding and signal transduction can take place even with a molecule having blocked the C-terminus of the alpha subunit. The carboxyl terminal of the alpha subunit has been shown to be involved in hormone binding and signal transduction of all the heterodimeric glycoprotein hormones. However, deletion of five amino acids from the C-terminus of the alpha subunit in the single chain hCG did not alter the overall conformation of the fusion molecule and its receptor binding ability, but led to a significant reduction in its ability to elicit biological response. These data show that these five amino acids at the C-terminus of the alpha subunit in the single chain hCG are not absolutely essential for attaining a conformation required for receptor binding, but are essential for obtaining a full biological response.
authors.affiliation: Department of Molecular Reproduction, Indian Institute of Science, Bangalore 560012, India.
authors.forename: C
authors.initials: C
authors.lastname: Sen Gupta
authors.forename: R R
authors.initials: RR
authors.lastname: Dighe
mesh_terms: D001681:Biological Assay; D002460:Cell Line; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D003001:Cloning, Molecular / Q000379:methods; D015292:Glycoprotein Hormones, alpha Subunit / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D007985:Leydig Cells / Q000187:drug effects; D008297:Male; D010843:Pichia; D016133:Polymerase Chain Reaction; D011869:Radioligand Assay; D011974:Receptors, LH / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000493:pharmacokinetics / Q000494:pharmacology
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D015292:Glycoprotein Hormones, alpha Subunit; D011974:Receptors, LH; D011993:Recombinant Fusion Proteins