The histones of the sperm of Spisula solidissima include a novel, cysteine-containing H-1 histone

Abstract

The histones remaining at the end of the spermiogenic differentiation, which are found associated with a highly basic protamine-like component [Ausio, J. and K.E. Van Holde (1987) Eur. J. Biochem. 165, 363–371] in the mature sperm of Spisula solidissima, have been isolated and characterized for the first time. All four core histones H2A, H2B, H3, H4, and the lysine-rich histone H1 are present. The core histones are found in equal stoichiometric amounts. As has been observed in other bivalve molluscs, the amino acid compositions of the core histones of S. solidissima sperm are very close to those of their counterparts in the calf thymus somatic histones. The spermatic histone H1 exhibits an amino acid composition and structural features similar to other histones of the histone H1 family. Yet this latter histone seems to be sperm-specific, and it contains at least two cysteine residues per molecule, which makes it unique in its class.