The Biosynthesis of Protamine in Trout Testis

This is the authors' abstract. We don't add key points for this paper.

After completion of the synthesis of protamine in the cytoplasm of rainbow trout testis spermatid cells, the seryl residues of the molecule are phosphorylated (Ingles, C. J., and Dixon, G. H. (1967) Proc. Nat. Acad. Sci. U. S. A., 58, 1011). Amino acid sequence studies (Ando, T., and Watanabe, S. (1969) Int. J. Protein Res., 1, 22) of three components of rainbow trout protamine each containing 4 seryl residues show that 3 seryl residues occur together in the NH2-terminal half of each protamine in the sequence Arg-Ser-Ser-Ser-Arg and the 4th in the COOH-terminal half of the molecule in the sequence Val-Ser-Arg. It is shown here that tryptic phosphopeptides in which each seryl residue is recovered in the phosphorylated form can be isolated from protamine labeled with [32P]phosphate in vivo. In addition, a further series of phosphoseryl peptides corresponding to the sequence Arg-Ser(PO4)-Ser(PO4)-Arg have been isolated, and it is suggested that these are derived from an as yet unsequenced component of rainbow trout protamine. An ionophoretic method for determining whether a given seryl residue is phosphorylated is also described.