Molecular evolution of cytochrome c oxidase subunit .4. Evidence for positive selection in simian primates
Molecular evolution of cytochrome c oxidase subunit .4. Evidence for positive selection in simian primates
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DOI：
10.1007/pl00006172
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发表时间：
1997-05-01
影响因子：
3.9
通讯作者：
Grossman, LI
中科院分区：
文献类型：
--
作者：
Wu, W;Goodman, M;Grossman, LI
细胞色素c氧化酶(COX)是一种多亚单位酶复合体，通过线粒体内膜呼吸链催化电子传递的最后一步。线粒体(亚基I、亚基II和亚基III)和核基因组编码的多达13个亚基存在于从酵母到人类的真核生物中。以前，我们观察到与小鼠、大鼠和牛的同源基因相比，人COX IV亚基中有大量的氨基酸替换。在这里，我们研究了两组类人型灵长类动物，卡他类动物(人科，脑石类)和颈角类灵长类动物(头骨动物)，以及一种原猴灵长类动物(Lorisiform)的COXIV进化，方法是从基因组DNA中测序COX4基因的部分功能片段。对COX4序列数据的系统发育分析表明，加速的非同义替换率在卡他类和鸭嘴兽的早期进化中都很明显，程度较小。这些加速的速率之后是减速的，这表明适应性氨基酸替换的正选择变成了净化选择，保留了已经发生的替换。正向选择的证据在卡他类到类人科的谱系中尤其明显，在这种谱系中，非同义词的比率先是快于同义词的比率，然后又慢得多。三种类型的中性DNA核苷酸替换(同义替换、假基因核苷酸替换和内含子核苷酸替换)的比率相似，并与先前观察到的人的核基因组中此类替换的速度慢于其他灵长类和哺乳动物的核基因组的观察结果一致。
Cytochrome c oxidase (COX) is a multisubunit enzyme complex that catalyzes the final step of electron transfer through the respiratory chain on the mitochondrial inner membrane. Up to 13 subunits encoded by both the mitochondrial (subunits I, II, and III) and nuclear genomes occur in eukaryotic organisms ranging from yeast to human. Previously, we observed a high number of amino acid replacements in the human COX IV subunit compared to mouse, rat, and cow orthologues. Here we examined COX IV evolution in the two groups of anthropoid primates, the catarrhines (hominoids, cercopithecoids) and platyrrhines (ceboids), as well as one prosimian primate (lorisiform), by sequencing PCR-amplified portions of functional COX4 genes from genomic DNAs. Phylogenetic analysis of the COX4 sequence data revealed that accelerated nonsynonymous substitution rates were evident in the early evolution of both catarrhines and, to a lesser extent, platyrrhines. These accelerated rates were followed later by decelerated rates, suggesting that positive selection for adaptive amino acid replacement became purifying selection, preserving replacements that had occurred. The evidence for positive selection was especially pronounced along the catarrhine lineage to hominoids in which the nonsynonymous rate was first faster than the synonymous rate, then later much slower. The rates of three types of ''neutral DNA'' nucleotide substitutions (synonymous substitutions, pseudogene nucleotide substitutions, and intron nucleotide substitutions) are similar and are consistent with previous observations of a slower rate of such substitutions in the nuclear genomes of hominoids than in the nuclear genomes of other primate and mammalian lineages.