X-ray crystallographic studies on molecular mechanism of Oxygen respriration

测定了不同状态下牛心细胞色素C氧化酶的晶体结构。完全氧化态的分辨率为2.3*，完全还原状态为2.35*，CO结合的完全还原状态为2.8*；全氧化酶在2.3*分辨率下的晶体结构分析表明：(1)过氧化基连接Fea3和Cub双核中心是氧还原位，(2)Cub的配体之一His240与Tyr244通过共价键相连，(3)存在提供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a-螺旋在7%的甘氨酸残基中丰富，全还原酶在2.35*分辨率下的晶体结构分析表明：(1)氧还原位没有配体，(2)亚基I的Gly49-Asn55残基在还原状态下与氧化状态下的残基构象不同。叠氮结合氧化形式的晶体结构分析表明：(1)叠氮基团结合在酶的氧还原位和分子表面，(2)与CuB连接的所有组氨酸残基不具有与细菌酶相反的多构象状态。

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.