# Biological activity of Single chain Choriogonadotropin, $hCG \alpha \beta$ is decreased upon deletion of five Carboxyl terminal amino acids of the $\alpha$ subunit without affecting its receptor binding

Gupta, CS and Dighe, RR (2000) Biological activity of Single chain Choriogonadotropin, $hCG \alpha \beta$ is decreased upon deletion of five Carboxyl terminal amino acids of the $\alpha$ subunit without affecting its receptor binding. In: Journal of Molecular Endocrinology, 24 (2). pp. 157-164.

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## Abstract

The strategy of translationally fusing the two subunits of human Choriogonadotropin (hCG) has been used to produce recombinant single chain hCG in which the C terminus of the a subunit is fused to the N terminus $\beta$ without any linker using Pichia pastoris expression system. The Pichia expressed $hCG\alpha \beta$ $(phCG\alpha \beta)$ attained an overall conformation similar to that of hCG, 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 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.

Item Type: Journal Article Copyright of this article belongs to Society for Endocrinology Biochemistry and Molecular Biophysics Division of Biological Sciences > Molecular Reproduction, Development & Genetics (formed by the merger of DBGL and CRBME) 01 Oct 2007 19 Sep 2010 04:39 http://eprints.iisc.ernet.in/id/eprint/12018