Ma D P, Zharkikh A, Graur D, VandeBerg J L, Li W H
Department of Biochemistry and Molecular Biology, Mississippi State University 39762.
J Mol Evol. 1993 Apr;36(4):327-34. doi: 10.1007/BF00182180.
We have sequenced the mitochondrial cytochrome b gene from the guinea pig, the African porcupine, and a South American opossum. A phylogenetic analysis, which includes 22 eutherian and four other vertebrate cytochrome b sequences, indicates that the guinea pig and the porcupine constitute a natural clade (Hystricomorpha) that is not a sister group to the clade of mice and rats (Myomorpha). Therefore, the hypothesis that the Rodentia is paraphyletic receives additional support. The artiodactyls, the perissodactyls, and the cetaceans form a group that is separated from the primates and the rodents. The 26 sequences are used to study the structure/function relationships in cytochrome b, whose function is electron transport. Most of the amino acid residues involved in the two reaction centers are well conserved in evolution. The four histidines that are believed to ligate the two hemes are invariant among the 26 sequences, but their nearby residues are not well conserved in evolution. The eight transmembrane domains represent some of the most divergent regions in the cytochrome b sequence. The rate of nonsynonymous substitution is considerably faster in the human and elephant lineages than in other eutherian lineages; the faster rate might be due to coevolution between cytochrome b and cytochrome c.
我们已经对豚鼠、非洲豪猪和一种南美负鼠的线粒体细胞色素b基因进行了测序。一项系统发育分析纳入了22种真兽亚纲动物以及其他4种脊椎动物的细胞色素b序列，结果表明豚鼠和豪猪构成一个自然分支（豪猪亚目），它并非小鼠和大鼠所在分支（鼠形亚目）的姐妹群。因此，啮齿目是并系群这一假说得到了更多支持。偶蹄目动物、奇蹄目动物和鲸目动物形成一个与灵长目动物和啮齿动物相分离的类群。这26个序列被用于研究细胞色素b的结构/功能关系，其功能是电子传递。参与两个反应中心的大多数氨基酸残基在进化过程中高度保守。被认为与两个血红素相连的4个组氨酸在这26个序列中是不变的，但它们附近的残基在进化过程中保守性不强。8个跨膜结构域是细胞色素b序列中一些差异最大的区域。在人类和大象谱系中，非同义替换的速率比其他真兽亚纲谱系快得多；较快的速率可能是由于细胞色素b和细胞色素c之间的协同进化。
