Sperm nuclei of Discoglossus pictus (anuran amphibian) contain a unique, histidine-rich basic protein

Fractionation with reverse-phase HPLC and electrophoretic analyses revealed that the nuclear basic proteins in sperm of an anuran amphibian, Discoglos sus pictus, consisted of weakly basic proteins without histones. Amino acid analyses indicated that none of these proteins were histones or protamines because of the low amounts of Lys and Arg. The predominant protein among t hose fractionated possessed an unusually high content of His and extremely low amounts of Arg and Lys, indicating that this is a unique nuclear basic protein not reported previously. The induction of a highly decondensed stat e of sperm nuclei upon their incubation in egg extract was accompanied by t he removal of most, if not all, of this His-rich protein from the nuclei.