Heme-heme communication during the alkaline-induced structural transition in cytochrome c oxidase.
Heme-heme communication during the alkaline-induced structural transition in cytochrome c oxidase.
复制标题
细胞色素 c 氧化酶碱诱导结构转变期间血红素-血红素通讯。
DOI：
10.1016/j.jinorgbio.2007.11.004
复制
发表时间：
2008
影响因子：
3.9
通讯作者：
Yeh,Syun-Ru
中科院分区：
文献类型：
--
作者：
Ji,Hong;Rousseau,DenisL;Yeh,Syun-Ru
Alkaline-induced conformational changes at pH 12.0 in the oxidized as well as the reduced state of cytochrome c oxidase have been systematically studied with time-resolved optical absorption and resonance Raman spectroscopies. In the reduced state, the heme a3first converts from the native five-coordinate configuration to a six-coordinate bis-histidine intermediate as a result of the coordination of one of the CuBligands, H290 or H291, to the heme iron. The coordination state change in the heme a3causes the alteration in the microenvironment of the formyl group of the heme a3and the disruption of the H-bond between R38 and the formyl group of the heme a. This structural transition, which occurs within 1min following the initiation of the pH jump, is followed by a slower reaction, in which Schiff base linkages are formed between the formyl groups of the two hemes and their nearby amino acid residues, presumably R38 and R302 for the heme a and a3, respectively. In the oxidized enzyme, a similar Schiff base modification on heme a and a3was observed but it is triggered by the coordination of the H290 or H291 to heme a3followed by the breakage of the native proximal H378-iron and H376-iron bonds in heme a and a3, respectively. In both oxidation states, the synchronous formation of the Schiff base linkages in heme a and a3relies on the structural communication between the two hemes via the H-bonding network involving R438 and R439 and the propionate groups of the two hemes as well as the helix X housing the two proximal ligands, H378 and H376, of the hemes. The heme–heme communication mechanism revealed in this work may be important in controlling the coupling of the oxygen and redox chemistry in the heme sites to proton pumping during the enzymatic turnover of CcO.
