Calvin H I
Biochim Biophys Acta. 1976 Jun 15;434(2):377-89. doi: 10.1016/0005-2795(76)90229-4.
Cysteine-rich protamines (Arg = 47-61%, Cys = 8-16%) were isolated from the sperm of an individual guinea pig, human and rabbit and from pooled samples of mouse and rat sperm. Appreciable concentrations of histones were not found in the sperm nuclei of these species. In addition to the protamines, a substance of relatively low molecular weight, which reacted with the Lowry reagent, appeared in crude acid-soluble extracts of sperm nucleoprotein. This unidentified contaminent was resolved from the protamines by chromatography on Bio-Rex 70. Heterogeneity of human and mouse protamines was revealed by electrophoresis at pH 2.7, in the presence of 2.5 M urea, and confirmed by amino acid analysis, which also suggested the presence of 2 or more species of protamine in the rabbit. By contrast, the guinea pig and rat preparations displayed nearly stoichiometric ratios of amino acid residues, approaching homogeneity by this criterion. The functional consequences of crosslinks between cysteine residues of these proteins and the possible species-specific significance of their differing percentages of histidine are discussed. Potentially analogous functions are suggested for phosphorylated serine and threonine, and for ionized cysteine and tyrosine, within the protamines of developing spermatids. Their amino acid compositions indicate that the protamines of eutherian mammals are coded by a C.G-rich genome which has been unusually susceptible to genetic drift. An especially high rate of G leads to A transitions seems to have occurred in the human protamine genes.
从一只豚鼠、人类和兔子的精子以及小鼠和大鼠精子的混合样本中分离出富含半胱氨酸的鱼精蛋白（精氨酸含量为47 - 61%，半胱氨酸含量为8 - 16%）。在这些物种的精子细胞核中未发现可观浓度的组蛋白。除了鱼精蛋白外，一种相对低分子量且能与洛瑞试剂反应的物质出现在精子核蛋白的粗酸溶性提取物中。通过在Bio - Rex 70上进行色谱分离，这种未鉴定的污染物与鱼精蛋白得以分离。在pH 2.7、存在2.5 M尿素的条件下进行电泳，揭示了人类和小鼠鱼精蛋白的异质性，氨基酸分析证实了这一点，氨基酸分析还表明兔子中存在两种或更多种鱼精蛋白。相比之下，豚鼠和大鼠的制剂显示出氨基酸残基接近化学计量比，据此标准接近同质性。讨论了这些蛋白质半胱氨酸残基之间交联的功能后果以及它们不同组氨酸百分比可能具有的物种特异性意义。对于发育中的精子细胞鱼精蛋白中的磷酸化丝氨酸和苏氨酸，以及离子化的半胱氨酸和酪氨酸，提出了潜在的类似功能。它们的氨基酸组成表明，真兽亚纲哺乳动物的鱼精蛋白由富含C.G的基因组编码，该基因组对遗传漂变异常敏感。在人类鱼精蛋白基因中似乎发生了特别高的从G到A的转换率。
