[Primary structure of the basic nuclear protein from spermatozoa of the mollusk Illex argentinus and its comparison with the structure of sperm proteins in other animals].

The spermatic protein of chromatin I2 of squid Illex argentinus was separated by HPLC into two components I2-1 and I2-2. Amino acid sequences of the major portion of protein I2-1 (52 residues) and the N-terminal sequence of protein I2-2 (21 residues) were determined. Arginines in protein I2-1 are arranged in clusters typical of protamines; the first cluster is in the N-terminus, the longest heterogeneous basic cluster is in the central part of the protein chain, the C-terminal part of the molecule contains two clusters of three hydroxyamino acids each. The N-terminal sequences of illexins I2-1 and I2-2 (1-14 residues) are highly homologous. Homologous regions were found in illexin I2-1, tunnin of tuna fish and avian gallin thus defining the notion of proteins of an intermediate type from mollusc spermatozoa chromatin exemplified by the squid protamine-like protein.