pH-dependent structural changes at the heme-copper binuclear center of cytochrome c oxidase
pH-dependent structural changes at the heme-copper binuclear center of cytochrome c oxidase
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DOI：
10.1016/s0006-3495(01)76177-2
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发表时间：
2001-05-01
影响因子：
3.4
通讯作者：
Rousseau, DL
中科院分区：
文献类型：
--
作者：
Das, TK;Tomson, FL;Rousseau, DL
球形红杆菌AA(3)细胞色素C氧化酶的共振拉曼光谱揭示了室温下双核位置随pH变化的结构。从完全还原的酶的CO络合物的共振拉曼光谱中明显不同的Fe-CO伸缩模式可以看出，该酶的催化中心双核中心在中性pH下具有两种构象。两种构象(α和β)在pH 6-9范围内可逆相互转换，pKa为7.4，与在低温下进行的傅立叶变换红外光谱测量一致(D.M.Mitchell，J.P.Shapleigh，A.M.Archer，J.O.Alben和R.B.Gennis，1996，生物化学35：9446-9450)。推测不同的结构是由于在双核中心附近存在一个或多个可电离基团而导致铜-B原子相对于CO的位置发生变化。与氧结合口袋相邻的保守酪氨酸残基(球形罗氏杆菌中的Tyr-288，牛酶中的Tyr-244)或与铜-B配位的组氨酸之一是可能的候选者。在生理pH和室温下，这两种构象之间存在平衡，这表明它们可能在功能上参与了酶的活性。
The resonance Raman spectra of the aa(3) cytochrome c oxidase from Rhodobacter sphaeroides reveal pH-dependent structural changes in the binuclear site at room temperature. The binuclear site, which is the catalytic center of the enzyme, possesses two conformations at neutral pH, assessed from their distinctly different Fe-CO stretching modes in the resonance Raman spectra of the CO complex of the fully reduced enzyme. The two conformations (alpha and beta) interconvert reversibly in the pH 6-9 range with a pKa of 7.4, consistent with Fourier transform infrared spectroscopy measurements done at cryogenic temperatures (D. M. Mitchell, J. P. Shapleigh, A. M. Archer, J. O. Alben, and R. B. Gennis, 1996, Biochemistry 35:9446-9450). It is postulated that the different structures result from a change in the position of the Cu-B atom with respect to the CO due to the presence of one or more ionizable groups in the vicinity of the binuclear center. The conserved tyrosine residue (Tyr-288 in R. sphaeroides, Tyr-244 in the bovine enzyme) that is adjacent to the oxygen-binding pocket or one of the histidines that coordinate Cu-B are possible candidates. The existence of an equilibrium between the two conformers at physiological pH and room temperature suggests that the conformers may be functionally involved in enzymatic activity.