X-ray crystallographic studies on molecular mechanism of Oxygen respriration

测定了牛心细胞色素c氧化酶不同状态的晶体结构。完全氧化态的分辨率为2.3*，完全还原态的分辨率为2.35*，CO结合完全还原态的分辨率为2.8* ;叠氮化物结合的完全氧化态，2.9*。在2.3* 分辨率下的完全氧化的酶的晶体结构分析揭示了（1）过氧化物基团桥接Fea 3和CuB双核中心，其是氧还原位点，（2）His 240，CuB的配体之一和Tyr 244通过共价键连接，（3）存在促进电子和质子转移的水分子，（4）Na或Ca离子位于酶分子内，（5）酶形成由心磷脂分子稳定的二聚体结构，（6）跨膜α-螺旋在甘氨酸残基中丰富，为7%，在2.35* 分辨率下对完全还原的酶的晶体结构分析阐明了（1）氧还原位点没有配体，（2）还原态I亚基Gly 49至Asn 55残基与氧化态残基的构象不同。CO结合完全还原酶2.8* 的晶体结构分析在2.9* 分辨率下对叠氮键合的氧化形式的晶体结构分析表明，（1）叠氮基结合在酶的氧还原位点和分子表面，和（2）所有连接到CuB上的组氨酸残基与细菌酶的组氨酸残基相比不具有多个构象状态。

Crystal structures of cytochome c oxidase from bovine heart at various states are determined. Fully oxidized state was at 2.3*resolution ; fully reduced state, 2.35* ; CO bound fully reduced state, 2.8* ; azide bound fully oxidized state, 2.9*.Crystal structure analysis of the fully oxidized enzyme at 2.3* resolution revealed that (1) a peroxide group bridges Fea3 and CuB dinuclear center which is an oxygen reduction site, (2) His240, one of the ligands of CuB,and Tyr244 are linked by a covalent bond, (3) there exist water molecules contributing electron and proton transfer, (4) Na or Ca ions are located within the enzyme melecule, (5) the enzyme forms dimeric structure stabilized by cardiolipin molecules, (6) trans-membrane a-helices are abundant in glycine residues at 7%, which do not break a-helices.Crystal structure analysis of fully reduced enzyme at 2.35* resolution elucidated that (1) the oxygen reduction site has no ligand, (2) the residues fro Gly49 to Asn55 of subunit I in reduced state are different from those in oxidized state in their conformation.Crystal structure analysis of the CO bound fully reduced enzyme at 2.8* resolution revealed that (1) CO group ligates Fea3, and (2) the residues Gly49 to Asn55 of subunit I are similar to those of the reduced state in their conformation.Crystal structure analysis of the azide bound oxidized form at 2.9* resolution revealed that (1) azide groups bound at the oxygen reduction site and a molecular surface of the enzyme, and (2) all the histidine residues which ligate to the CuB do not have multiple conformational states in contrast to those of the bacterial enzyme.