精制金枪鱼细胞色素c中的氧化还原构象变化
Redox conformation changes in refined tuna cytochrome c.
作者信息
Takano T, Dickerson R E
出版信息
Proc Natl Acad Sci U S A. 1980 Nov;77(11):6371-5. doi: 10.1073/pnas.77.11.6371.
Tuna ferrocytochrome c and ferricytochrome c have been refined independently at high resolution (1.5 A and 1.8 A) to crystallographic residual errors of 17.3% and 20.8%, respectively. Small but significant conformational differences are seen surrounding a buried water molecule that is hydrogen bonded to Asn-52, Tyr-67, and Thr-78. In the oxidized state, this water molecule is 1.0 A closer to the heme and the heme has moved 0.15 A out of its heme crevice; both changes lead to a more polar microenvironment for the heme. Chemical modification studies, patterns of evolutionary conservatism, structural differences in bacterial cytochromes, and x-ray studies all agree that the "active site" for cytochrome c is bounded by lysines 8, 13,27, 72, 79, 86, and 87 (thus containing the evolutionary conservative 72-87 loop) and has the buried water molecule just below its surface and the opening of the heme crevice slightly to one side.
金枪鱼亚铁细胞色素c和高铁细胞色素c已分别在高分辨率（1.5埃和1.8埃）下独立精修，晶体学残余误差分别为17.3%和20.8%。在与天冬酰胺-52、酪氨酸-67和苏氨酸-78形成氢键的一个埋藏水分子周围，可见微小但显著的构象差异。在氧化状态下，这个水分子距离血红素近1.0埃，且血红素已从其血红素裂隙中移出0.15埃；这两个变化都导致血红素的微环境更具极性。化学修饰研究、进化保守模式、细菌细胞色素的结构差异以及X射线研究均一致认为，细胞色素c的“活性位点 ”由赖氨酸8、13、27、72、79、86和87界定（因此包含进化保守的72 - 87环），且在其表面下方有埋藏的水分子，血红素裂隙的开口略向一侧。
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