Bolgiano B, Salmon I, Ingledew W J, Poole R K
Microbial Physiology Research Group, Kings College London, U.K.
Biochem J. 1991 Mar 15;274 ( Pt 3)(Pt 3):723-30. doi: 10.1042/bj2740723.
Potentiometric analyses of the cytochrome o-type oxidase of Escherichia coli, using membranes from a strain containing amplified levels of the cytochrome bo complex, were conducted to resolve the redox centres of the oxidase. The cytochrome o-type oxidase of E. coli, a quinol oxidase, contains 2 mol of b-type haem per mol of complex and copper. Detailed analysis of potentiometric titrations, based on the absorbance of the Soret band, suggests that there are three contributions with midpoint potentials (Em,7) around +55 mV, +211 mV and +408 mV, all with maxima at 426-430 nm in the reduced state. In the alpha region of the spectra, a component with Em,6.85 = +58 mV has a maximal peak at 557 nm, and twin peaks at 556 and 564 nm nitrate with Em,6.85 = +227 mV. A feature corresponding to the highest potential Soret contribution was not observed. These data can be explained either by a model incorporating haem-haem interaction or by attributing the shorter-wavelength band (557 nm) to haem b and a split alpha-band (556, 564 nm) to the haem o (oxygen-binding haem b). Absolute spectra of oxidized membranes show continuous absorbance from 460 to 530 nm and suggest the presence of a high-spin haem component in the membranes. Monitoring absorbance at 635 minus 672 nm, contributions with midpoints (Em,7) around +52 mV, +234 mV and +371 mV are observed. This latter contribution is possibly the highest-potential component which titrates with Em greater than +400 mV in the Soret region and may represent copper-haem coupling in the cytochrome o complex.
利用来自一株细胞色素bo复合物水平扩增的菌株的膜，对大肠杆菌细胞色素o型氧化酶进行了电位分析，以解析该氧化酶的氧化还原中心。大肠杆菌的细胞色素o型氧化酶是一种喹啉氧化酶，每摩尔复合物含有2摩尔b型血红素和铜。基于Soret带吸光度的电位滴定详细分析表明，存在三种贡献，其中点电位（Em,7）分别约为+55 mV、+211 mV和+408 mV，在还原态下均在426 - 430 nm处有最大值。在光谱的α区域，Em,6.85 = +58 mV的一个组分在557 nm处有一个最大峰，而Em,6.85 = +227 mV的硝酸盐在556和564 nm处有双峰。未观察到与最高电位Soret贡献相对应的特征。这些数据可以通过包含血红素 - 血红素相互作用的模型来解释，或者通过将较短波长带（557 nm）归因于血红素b，将分裂的α带（556、564 nm）归因于血红素o（氧结合血红素b）来解释。氧化膜的绝对光谱在460至530 nm处显示出连续吸光度，表明膜中存在高自旋血红素组分。监测635减去672 nm处的吸光度，观察到中点（Em,7）约为+52 mV、+234 mV和+371 mV的贡献。后一种贡献可能是最高电位组分，其在Soret区域中Em大于+400 mV时滴定，可能代表细胞色素o复合物中的铜 - 血红素偶联。
