ISOLATION AND PROPERTIES OF A PROTEIN COMPLEX CONTAINING FLAGELLAR MOVEMENT-INITIATING PHOSPHOPROTEIN FROM TESTES OF A WHITE SALMON

Phosphorylation of a tyrosine residue within a 15-kDa protein has been found to play a role in the initiation of flagellar movement of quies cent spermatozoa of the rainbow trout, Salmo gairdneri [Morisawa and H ayashi (1986) Biomed. Res. 6, 181-184; Hayashi et al. (1987) J. Biol. Chem. 262, 16692-16698]. In order to find a more accessible source of the 15-kDa protein for biochemical studies, phosphorylation of protein s was studied in other organs from other species. Cell-free extracts f rom spermatozoa and testes of Salmonidae were prepared and all catalyz ed the cAMP-dependent, Mg2+-requiring, but Ca2+-independent phosphoryl ation of the 15-kDa proteins. Protein from the testes of a white salmo n, Oncorhynchus keta, was isolated by conventional purification method s. The 15-kDa protein in the cell-free extract was found to be complex ed with several other proteins such that the 15-kDa protein and its ph osphorylating activity were copurified. Isolation of a sufficient amou nt of the complex for the preparation of antibodies against the variou s constituents is now possible.