title: Expression and characterization of recombinant beta-subunit hCG homodimer.
abstract: We have linked two human chorionic gonadotropin (hCG) beta-subunit cDNAs in tandem such that the expressed fusion protein consists of two mature beta-subunits joined through the carboxy terminal peptide of the first beta-subunit. A single glycine residue is inserted between the two subunits in the fusion protein. Chinese hamster ovary (CHO) cells transformed with a clone that contains the fused cDNAs express and secrete a protein that is consistent with it being a beta-hCG homodimer protein. These beta-homodimer molecules can recombine with two free alpha-subunits indicating that both beta-subunits within the homodimer are likely folded in their native conformation. Our data also suggest that the two beta-subunits fold upon each other as a globular protein and do not appear to exist as a simple fusion of two linear beta-subunits. Furthermore, the two beta-monomer subunits in the fusion protein form a stable homodimer that can bind and activate the hLH/CG receptor specifically. Recombination of the fusion protein with alpha-subunits appears to favor an arrangement where two alpha-subunits combine with a single molecule of the fusion protein. The recombined molecule consists of four subunits and is comparable to two tethered hCG moieties, which constitutes a hCG dimer. This hormone dimer can bind and activate the hLH/CG receptor with an activity approximating that of native hCG.
authors.affiliation: Department of Obstetrics and Gynecology, Center for Reproductive Sciences, Columbia University, New York, NY 10032, USA.
authors.forename: L
authors.initials: L
authors.lastname: Lobel
authors.forename: S
authors.initials: S
authors.lastname: Pollak
authors.forename: S
authors.initials: S
authors.lastname: Wang
authors.forename: M
authors.initials: M
authors.lastname: Chaney
authors.forename: J W
authors.initials: JW
authors.lastname: Lustbader
mesh_terms: D000818:Animals; D015153:Blotting, Western; D016466:CHO Cells; D018997:Chorionic Gonadotropin, beta Subunit, Human / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D006224:Cricetinae; D019281:Dimerization; D015870:Gene Expression; D015292:Glycoprotein Hormones, alpha Subunit / Q000737:chemistry; D006801:Humans; D008958:Models, Molecular; D011487:Protein Conformation; D011974:Receptors, LH / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism
chemical_list: D018997:Chorionic Gonadotropin, beta Subunit, Human; D015292:Glycoprotein Hormones, alpha Subunit; D011974:Receptors, LH; D011993:Recombinant Fusion Proteins