Identification of 36-kDa flagellar phosphoproteins associated with hamster sperm motility

In our previous paper [M. Fujinoki et al. (2001) Biomed. Res. 22, 45-58], we reported that two types of 36-kDa protein, which were designated as 36K-A protein and 36K-B protein, obtained from hamster sperm flagella were phosphorylated at serine residues associated with the regulation of motility activation. In the present experiments, it was suggested that these two types of 36-kDa protein were phosphorylated in a cAMP-dependent manner associated with motility activation of hamster spermatozoa. Because the 36K-B protein was the most intensely phosphorylated in a cAMP-dependent manner, attempts were made to further characterize it. The 36K-B protein was assumed to be localized in the middle piece. The localization of the 36K-B protein was the same as that of the 36-kDa protein reported in our previous paper [Y. Si et al. (1999) Mol. Reprod. Dev. 52, 328-334]. In order to identify the 36K-B protein, it was analyzed by peptide mass finger printing and amino acid sequencing. The results suggested that the 36K-B protein was a pyruvate dehydrogenase E1 component beta subunit and a component of the mitochondrial sheath of the middle piece.