Glover C V, Gorovsky M A
Proc Natl Acad Sci U S A. 1979 Feb;76(2):585-9. doi: 10.1073/pnas.76.2.585.
A partial amino-acid sequence of Tetrahymena histone H4 has been determined and differs significantly from the sequence of calf or pea H4. The amino terminus of Tetrahymena H4, unlike that of other H4s so far examined, is not acetylated. Of 66 residues determined, one is a single-residue insertion, one a single-residue deletion, and thirteen are amino-acid replacements with respect to the calf thymus H4 sequence. Most of the amino-acid replacements are nonconservative and are distributed nonrandomly, with a strong concentration in the amino-terminal arm. The first four lysines are partially acetylated. All but two of the replacements can be explained by single nucleotide substitutions at the level of the gene. The similarity in sequence of calf and pea H4 coupled with the substantial differences displayed by Tetrahymena H4 suggest that the divergence of protozoa and higher eukaryotes substantially antedates the divergence of plants and animals. Furthermore, quantitative analysis of the data requires either that the rate of H4 evolution be considerably more rapid than previously thought or that the rate be different for different periods of evolution or for different lines of descent.
已经确定了四膜虫组蛋白H4的部分氨基酸序列，该序列与小牛或豌豆H4的序列有显著差异。与迄今为止检测的其他H4不同，四膜虫H4的氨基末端没有被乙酰化。在已确定的66个残基中，一个是单残基插入，一个是单残基缺失，相对于小牛胸腺H4序列，有13个是氨基酸替换。大多数氨基酸替换是非保守的，且分布不随机，在氨基末端臂中有很强的集中性。前四个赖氨酸部分被乙酰化。除了两个替换外，所有替换都可以通过基因水平上的单核苷酸替换来解释。小牛和豌豆H4序列的相似性，以及四膜虫H4显示出的显著差异，表明原生动物和高等真核生物的分化大大早于动植物的分化。此外，对数据的定量分析要求要么H4进化速率比以前认为的要快得多，要么不同进化时期或不同谱系的进化速率不同。
