竹叶青蛇毒腺磷脂酶A2同工酶的加速进化
Accelerated evolution of Trimeresurus flavoviridis venom gland phospholipase A2 isozymes.
作者信息
Nakashima K, Ogawa T, Oda N, Hattori M, Sakaki Y, Kihara H, Ohno M
机构信息
Department of Chemistry, Faculty of Science, Kyushu University, Fukuoka, Japan.
出版信息
Proc Natl Acad Sci U S A. 1993 Jul 1;90(13):5964-8. doi: 10.1073/pnas.90.13.5964.
Six Trimeresurus flavoviridis (Habu snake) venom gland phospholipase A2 (PLA2) isozyme genes were found to consist of four exons and three introns and to encode proteins of 138 amino acid residues, including the signal sequence of 16 amino acid residues. Comparison of the nucleotide sequences showed that the introns are much more homologous than the protein-coding regions of exons except for the signal peptide-coding region of the first exon. The numbers of nucleotide substitutions per site (KN) for introns are approximately one-fourth of the numbers of nucleotide substitutions per synonymous site (KS) for the protein-coding regions, indicating that the introns are unusually conserved. The absence of an apparent functional role for the introns suggests that the protein-coding regions, except for the signal peptide-coding domains, have evolved at greater substitution rates than introns. The fact that the numbers of nucleotide substitutions per nonsynonymous site (KA) are close to or larger than KS values for relevant pairs of genes revealed that Darwinian-type accelerated substitutions have occurred in the protein-coding regions or exons. This is compatible with the presence of PLA2 species with diverse physiological activities in the venom.
发现六种竹叶青蛇（哈布蛇）毒腺磷脂酶A2（PLA2）同工酶基因由四个外显子和三个内含子组成，编码138个氨基酸残基的蛋白质，包括16个氨基酸残基的信号序列。核苷酸序列比较表明，除了第一个外显子的信号肽编码区外，内含子比外显子的蛋白质编码区具有更高的同源性。内含子每个位点的核苷酸替换数（KN）约为蛋白质编码区每个同义位点的核苷酸替换数（KS）的四分之一，这表明内含子异常保守。内含子缺乏明显的功能作用表明，除信号肽编码域外，蛋白质编码区的进化替换率高于内含子。相关基因对的每个非同义位点的核苷酸替换数（KA）接近或大于KS值，这一事实表明在蛋白质编码区或外显子中发生了达尔文式加速替换。这与毒液中存在具有多种生理活性的PLA2种类相符。
Zotero 插件