Homodimer formation by the individual subunits of bovine lutropin as determined by sedimentation equilibrium.
Although differing in their amino acid sequences, the folding patterns of the alpha and beta subunits of human choriogonadotropin are similar in the crystal structure of the HF-treated glycoprotein hormone. Each subunit forms a cystine-knot motif like that found in several growth factors that form homodimers and heterodimers. In order to ascertain if the alpha and beta subunits can self-associate, e.g. to form homodimers, sedimentation equilibrium at various glycoprotein concentrations and temperatures was used to study the subunits of bovine lutropin, which are expected to exhibit conformations like those of the choriogonadotropin subunits. Each subunit was found to form homodimers with Kd values of 0.3 and 0.1 mM for alpha and beta respectively at 37 degrees C. Self-association was weakly exothermic for alpha and endothermic for beta; entropic factors made a major contribution for each. It is unlikely that homodimer formation of either subunit would be physiologically important, although homodimers may form to some extent intracellularly because of the relatively high concentrations during biosynthesis.
Peng
K C
KC
Department of Biochemistry and Molecular Biology, University of Georgia, Athens 30602, USA.
Puett
D
D
Brewer
J M
JM
D000818:Animals; D002417:Cattle; D002499:Centrifugation, Density Gradient; D006063:Chorionic Gonadotropin / Q000737:chemistry; D019281:Dimerization; D006801:Humans; D007986:Luteinizing Hormone / Q000737:chemistry*; D015394:Molecular Structure; D008970:Molecular Weight; D011487:Protein Conformation; D013816:Thermodynamics
D006063:Chorionic Gonadotropin; D007986:Luteinizing Hormone