Chemical Differentiation of Nuclear Proteins during Spermatogenesis in the Salmon*, by Max Alfert, Ph.d

The characteristic morphogenetic changes which occur during sperm formation are at times accompanied by profound chemical alterations of the nuclear material. Thus it has been known since Miescher's pioneer studies during the 1870's (19) that nuclei in the immature salmon testis contain nucleohistones, while ripe salmon sperm contain nucleoprotamines. Basic proteins which are intermediate in composition between histones and protamines have been found in the sperm of some species (12, 18) while histones occur in others (11, 16); histones are generally also found in somatic nuclei of animals and higher plants (12). Both protamines and histones extracted from any type of material are not single compounds but represent mixtures of related substances (13, 23). All of those known to date form a spectrum of basic nuclear proteins among which the protamines represent the extreme in basicity and in simplicity of composition and structure. More recent studies on salmon sperm composition have generally confirmed Miescher's results except for the finding that he overestimated the non-protamine protein content of the sperm nuclei. Polfister and Mirsky (21) reported that nucleoprotamines account for 91 per cent of the nuclear mass, while other workers (15) even claimed that these nuclei consist exclusively of nucleoprotamine. Such findings are in marked contrast to those typical for somatic nuclei (e.g. reference 6) and nuclei of sea urchin sperm (8) in which an appreciable fraction--at least about 25 per cent--of non-histone protein occurs. Compared to other nuclear types, the sperm nuclei of the salmon and related fishes thus may be characterized by two separate biochemical peculiarities: (a) the extreme qualitative modification of the basic proteins to protamines consisting predominantly of arginine residues, and (b) the extreme quantitative reduction of other nuclear protein fractions. When both of these changes