Toro G C, Wernstedt C, Medina C, Jaramillo N, Hellman U, Galanti N
Department of Cell Biology and Genetics, School of Medicine, University of Chile, Santiago.
J Cell Biochem. 1992 Jul;49(3):266-71. doi: 10.1002/jcb.240490309.
Trypanosoma cruzi presents six histones electrophoretically resolved in three gel systems. Indirect evidence shows that one of these histones, named e, corresponds to H4 in other species. We present evidence that histone e is H4 by sequencing its amino terminal end. The amino terminal of T. cruzi histone H4, unlike that of other H4s examined thus far is not blocked. Moreover, this protein presents two variants. This partial amino acid sequence of T. cruzi histone H4 differs greatly from homologous sequences of human, yeast, or Tetrahymena. Since the conservatism of the core histones (H2A, H2B, H3, and H4) is clearly illustrated by comparative sequence analyses, the data shown here demonstrates that T. cruzi histone H4 is the most divergent reported. Quantitative analysis of the data suggests that the rate of substitutions in the histone H4 amino terminal sequence varies among different lineages. We postulate a slow-down in the evolutionary rate of histone H4 amino terminal domain in the metazoa branch related perhaps to the appearance of a novel function for this domain.
克氏锥虫呈现出六种可在三种凝胶系统中通过电泳分离的组蛋白。间接证据表明，其中一种名为e的组蛋白与其他物种中的H4相对应。我们通过对其氨基末端进行测序，证明组蛋白e就是H4。克氏锥虫组蛋白H4的氨基末端与迄今为止所检测的其他H4不同，它没有被封闭。此外，这种蛋白质存在两种变体。克氏锥虫组蛋白H4的这一氨基酸部分序列与人类、酵母或四膜虫的同源序列有很大差异。由于通过比较序列分析清楚地表明了核心组蛋白（H2A、H2B、H3和H4）的保守性，此处所示数据表明克氏锥虫组蛋白H4是已报道的差异最大的。对数据的定量分析表明，组蛋白H4氨基末端序列中的替换率在不同谱系中有所不同。我们推测后生动物分支中组蛋白H4氨基末端结构域的进化速率减缓，这可能与该结构域新功能的出现有关。
