The complete amino acid sequences of alpha subunits of chum salmon gonadotropins.

The complete amino acid sequences of alpha subunits of chum salmon (Oncorhynchus keta) gonadotropins (GTHs), GTH I and GTH II, were determined. Subunits were separated by reversed-phase high-performance liquid chromatography. Two alpha subunits, I alpha 1 and I alpha 2, were obtained from GTH I, whereas only one alpha subunit was obtained from GTH II. Sequence analysis revealed that GTH I alpha 2 is identical to GTH II alpha, but distinct from GTH I alpha 1. The I alpha 1 and II alpha consist of 95 and 92 amino acid residues, respectively. GTH I alpha 1 has 72% sequence identity with GTH I alpha 2. The two alpha subunits show approximately 65% sequence identity with bovine alpha subunit. This is the first finding of two chemically distinct alpha subunits from one species.