Evolution and Function of Primate Cytochrome c oxidase Gene

细胞色素c氧化酶(COX)在哺乳动物中由13个亚基组成，其中3个在线粒体DNA中编码，10个在核DNA中编码。分析单个亚基的进化模式可以建议进行功能测试，并可以作为多亚单位复合体进化的模型。在人类中，COX复合体在哺乳动物中是独一无二的，因为它缺乏第八亚单位的心脏亚型，而在灵长类动物的进化中，这一亚基显然在某个时候被沉默了。将确定其丢失的谱系，将分离和鉴定来自密切相关谱系的Cox8心脏和肝脏亚型的启动子区域，并将使用报告构建物来评估它们在分化和未分化成肌细胞中的组织特异性和活性。COX7A亚型基因具有线粒体靶向前序列，先前的研究结果表明其参与了组织特异性的亚型功能。这是意想不到的，因为前序列在线粒体导入过程中被移除，并被认为不参与COX功能。为了研究差异前序列功能的可能性，将在表达这两种异构体蛋白的细胞中检测每一种蛋白的细胞内位置。最后，将确定选定的三个核亚基的核苷酸替换率。COX提供了一个模型系统，以测试核基因的进化是否与与其结构接触或功能相互作用的线粒体基因的进化平行。

Cytochrome c oxidase (COX) comprises 13 subunits in mammals; three encoded in mitocondrial (mt) DNA and ten in nuclear DNA. Analysis of the evolution pattern of individual subunits can suggest tests of function and can serve as a model for the evolution of a multisubunit complex. In humans, the COX complex is unique among mammals in lacking the heart isoform of subunit VIII, which was apparently silenced sometime in primate evolution. The lineage in which it was lost will be identified, the promoter regions of COX8 heart and liver isoforms from closely related lineages will be isolated and characterized, and reporter constructs will be used to evaluate their tissue-specificity and activity in differentiated and undifferentiated myoblasts. COX7A isoform genes have mitochondrial targeting presequences which previous results suggest are involved in tissue-specific isoform function. This was unexpected because the presequences are removed during mitochondrial import and are thought not to participate in COX function. To investigate the potential for differential presequence function, the intracellular location of each of the two isoform proteins will be examined in cells that express both. Finally, the nucleotide substitution rates of three selected nuclear subunits will be determined.COX provides a model system to test whether evolution of nuclear genes is parallel to that of mitochondrial genes with which they come in structural contact or functionally interact.