[Lysine-rich histones of Crenomytilis grayanus].

Two lysin-rich histone fractions essentially differing in molecular weights were isolated from mature gonads of the Crenomytilis grayanus. Apart from differences in the length of the polypeptide chains, the proteins revealed some similar properties. They possess high positive charge due to a high content of lysin and arginine. Both histones are similar to histone H5 by the number of arginine, serine and alanine residues. Tyrosine residues essential for the tertiary structure of lysin-rich histones occupy similar positions in these proteins. The spatial structure of H1 molecules of Cr. grayanus is identical in terms of the size and amino acid composition of the globular fragments of both proteins. The larger size of one of the proteins is presumably due to an increased C-terminal domain enriched with lysine, alanine and proline residues. The presence of a globular region in the lysin-rich histones is indicative of a universal three-domain organization of histones H1 and H5. The presence of all the hydrophobic and the bulk of aromatic amino acids in this part of the molecule and certain rigidity of the amino acid composition as well as localization of the whole alpha-helix are typical for the proteins of the given class.