Primary Structure of a Protamine Isolated from the Sperm Nuclei of the Dog‐Fish Scylliorhinus caniculus

Abstract

A protamine was isolated from mature sperm nuclei of the dogfish S. caniculus. It contains 31 amino acids/molecule and only 5 types of residues: arginine (20), glycine (6), serine (3), alanine (1) and tyrosine (1). The primary structure of this protamine is reported. The N-terminal sequence contains the 4 hydroxylated amino acids of the molecule; the C-terminal region shows a sequence of 11 adjacent residues of arginine and contains all the glycine residues present in the protein. The structure of this scylliorhinine is compared to the amino acid sequence of other sperm protamines whose structure has been previously published. The presence of a modified tyrosine residue in some preparations is discussed in relation to sperm maturation.