Isolation and characterization of subunits from two distinct salmon gonadotropins.

Two distinct gonadotropins, GTH I and GTH II, isolated from female chum salmon pituitary glands, were separated into subunits by acid treatment and subsequent fractionation on reversed-phase high-performance liquid chromatography. GTH II was completely dissociated in 0.1% trifluoroacetic acid, while GTH I was partially dissociated. The acid-stable form of GTH I exhibited a potency identical to that of GTH I in stimulating estradiol-17 beta production in vitro. Both GTH I and GTH II consist of two dissimilar subunits. One subunit (alpha) is common to both GTHs, has Tyr as its N-terminal residue, and a molecular weight (Mr) of 22K by sodium dodecyl sulfate-polyacrylamide gel electrophoresis after reduction. The other subunit (beta) has a Mr of 17K and an N-terminal residue of Gly for GTH I, whereas GTH II beta is 18K and has an N-terminal residue of Ser, after reduction.