Identification and description of copper-thiolate vibrations in the dinuclear Cu-A site of cytochrome c oxidase
Identification and description of copper-thiolate vibrations in the dinuclear Cu-A site of cytochrome c oxidase
复制标题
DOI：
10.1021/ja960969g
复制
发表时间：
1996-10-30
影响因子：
15
通讯作者：
SandersLoehr, J
中科院分区：
文献类型：
--
作者：
Andrew, CR;Fraczkiewicz, R;SandersLoehr, J
细胞色素c氧化酶的Cu- a位点和铜氧毒素的1型Cu位点发生在具有His(2)Cys配体的同源蛋白群中，但其区别在于Cu- a中存在第二个Cys和第二个Cu，从而形成二硫酸桥接的双核Cu簇。反硝化副球菌可溶性含cu - a片段的共振拉曼（RR）谱在260和339 cm（-1）处表现出强烈的振动。它们各自的S-34同位素位移为-4.1和-5.1 cm(-1)，这使得它们被分配到Cu(2)S(2)Im(2)部分的两个Cu-S拉伸模式nu（Cu-S）。对被S、Cu和N同位素取代的Cu-A的RR光谱进行了正坐标分析（NCA），以确定是否有可能区分带有桥接或末端半胱氨酸配体的双核模型。而终端Cys模型预测nu（Cu-S）模式都在340到350 cm（-1）之间。桥接Cys几何结构成功地预测了260和339 cm（-1）处的s位移。因此，拉曼数据和NCA与x射线晶体学观察到的桥式半胱氨酸配位完全一致。通过在Cu2S2平面上下平移咪唑氮，使每个Cu原子形成扭曲的四面体，进一步提高了预测和观测到的振动同位素数据之间的一致性。由于与半胱氨酸配体的1酰胺振动的扩展振动耦合，I型蛋白的RR光谱高度依赖于n，而CUA中的振动对n同位素取代相对不敏感。因此，与1型Cu不同，仅用Cu2S2-(Im)(2)核心就可以成功地模拟CUA的RR谱。
The Cu-A site of cytochrome c oxidase and the type 1 Cu site of cupredoxins occur in homologous protein fords with a His(2)Cys ligand set, but the distinguished by the presence of a second Cys and a second Cu in Cu-A that result in the formation of a dithiolate-bridged dinuclear Cu cluster. The resonance Raman (RR) spectrum of the soluble Cu-A-containing fragment from Paracoccus denitrificans exhibits intense vibrations at 260 and 339 cm(-1). Their respective S-34-isotope shifts of -4.1 and -5.1 cm(-1) allow them to be assigned to two Cu-S stretching modes, nu(Cu-S), of the Cu(2)S(2)Im(2) moiety. A normal coordinate analysis (NCA) of the RR spectra of Cu-A substituted with isotopes of S, Cu, and N was carried out to determine whether it is possible to distinguish between dinuclear models with bridging or terminal cysteine ligands. Whereas the terminal Cys model predicts that both of the nu(Cu-S) modes lie between 340 and 350 cm(-1). the bridging Cys geometry successfully predicts the S-shifts at 260 and 339 cm(-1). Thus, the Raman data and NCA are fully consistent with the bridging cysteine coordination observed by X-ray crystallography. The agreement between predicted and observed vibrational isotope data is further improved by a trans-tilting of the imidazole nitrogens above and below the Cu2S2 plane, yielding a distorted tetrahedral geometry fur each of the Cu atoms. Whereas type I protein RR spectra are highly N-dependent due to extended vibronic coupling with 1 amide vibrations of the cysteine ligand, the vibrations in CUA are relatively insensitive to N-isotope substitution. Thus, unlike type 1 Cu, the RR spectrum of CUA can be successfully modeled with only the Cu2S2-(Im)(2) core.