Thomas J W, Puustinen A, Alben J O, Gennis R B, Wikström M
School of Chemical Sciences, University of Illinois, Urbana 61801.
Biochemistry. 1993 Oct 12;32(40):10923-8. doi: 10.1021/bi00091a048.
The terminal quinol oxidase, cytochrome bo, of Escherichia coli is a member of the large terminal oxidase family, which includes cytochrome aa3-type terminal oxidases from bacteria, plants, and animals. These enzymes conserve energy by linking electron transfer to vectorial proton translocation across mitochondrial or bacterial cell membranes. Site-directed mutagenesis of the five most highly conserved acidic amino acids in subunit I of cytochrome bo was performed to study their role in proton transfer. Mutation of only one of these sites, Asp135, to the corresponding amide, results in a dramatic decrease in proton pumping but with little change in electron-transfer activity. However, the conservative mutation Asp135Glu is active in proton translocation. It is proposed that an acidic residue at position 135 in subunit I may be important to form a functional proton input channel of the proton pump.
大肠杆菌的末端喹啉氧化酶细胞色素bo是大型末端氧化酶家族的成员，该家族包括来自细菌、植物和动物的细胞色素aa3型末端氧化酶。这些酶通过将电子传递与跨线粒体或细菌细胞膜的向量质子转运相联系来保存能量。对细胞色素bo亚基I中五个高度保守的酸性氨基酸进行定点诱变以研究它们在质子转移中的作用。这些位点中只有一个位点Asp135突变为相应的酰胺，会导致质子泵浦显著减少，但电子传递活性变化不大。然而，保守突变Asp135Glu在质子转运中具有活性。有人提出，亚基I中135位的酸性残基对于形成质子泵的功能性质子输入通道可能很重要。
