Aspartate-187 of cytochrome b is not needed for DCCD inhibition of ubiquinol: cytochrome c oxidoreductase in Rhodobacter sphaeroides chromatophores.
Aspartate-187 of cytochrome b is not needed for DCCD inhibition of ubiquinol: cytochrome c oxidoreductase in Rhodobacter sphaeroides chromatophores.
复制标题
DCCD 抑制泛醇：球形红细菌色素细胞中的细胞色素 c 氧化还原酶不需要细胞色素 b 的天冬氨酸 187。
DOI：
10.1021/bi001179t
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发表时间：
2000
期刊：
影响因子：
2.9
通讯作者：
Wraight,CA
中科院分区：
文献类型：
--
作者：
Shinkarev,VP;Ugulava,NB;Takahashi,E;Crofts,AR;Wraight,CA
N，N '-二环己基碳二亚胺（DCCD）可抑制细胞色素b1和b6 f复合物的稳态质子转运，而不显著改变电子传递速率，这一过程称为去偶联。在紫色细菌类球红细菌的色素体中，这与bc 1复合物细胞色素b亚基表面暴露的天冬氨酸-187的特异性标记有关[Wang et al.（1998）Arch. Biochem. Bioprotein. 352，193−198]。为了探索这个氨基酸残基在cytochromebc 1复合物质子反应中的可能作用，我们研究了DCCD修饰对类胡萝卜素在Rb中的电子传递和电致变色带移的影响。细胞色素b的天冬氨酸-187（AspB 187）已被改变为天冬酰胺（突变体B187 DN）。WT和B187 DN色素中类胡萝卜素电致变色位移的第III相的动力学和幅度，反映了bc 1复合物中的生电反应，以及细胞色素和反应中心的氧化还原变化，在WT和B187 DN色素中相似（± 15%）。DCCD有效地抑制了B187 DN和WT色素中类胡萝卜素带移的第三阶段。WT和B187 DN色素中，电致变色位移的第III相的动力学和振幅对DCCD浓度的依赖性是相同的，表明AspB 187的共价修饰并不专门负责细胞色素bc 1复合物的DCCD诱导效应。此外，没有证据表明差异抑制产电和电子传递被发现在任何菌株。我们的结论是AspB 187在bc 1复合物的质子反应中没有起关键作用，因为天冬酰胺取代AspB 187不会对bc 1复合物的产电反应产生任何显着影响，如类胡萝卜素电致变色转变的第三阶段所揭示的那样，或者对DCCD的营业额敏感性。
N,N‘-dicyclohexylcarbodiimide (DCCD) has been reported to inhibit steady-state proton translocation by cytochromebc1andb6fcomplexes without significantly altering the rate of electron transport, a process referred to as decoupling. In chromatophores of the purple bacteriumRhodobacter sphaeroides, this has been associated with the specific labeling of a surface-exposed aspartate-187 of the cytochromebsubunit of thebc1complex [Wang et al. (1998)Arch. Biochem. Biophys.352, 193−198]. To explore the possible role of this amino acid residue in the protonogenic reactions of cytochromebc1complex, we investigated the effect of DCCD modification on flash-induced electron transport and the electrochromic bandshift of carotenoids inRb. sphaeroideschromatophores from wild type (WT) and mutant cells, in which aspartate-187 of cytochromeb(AspB187) has been changed to asparagine (mutant B187 DN). The kinetics and amplitude of phase III of the electrochromic shift of carotenoids, reflecting electrogenic reactions in thebc1complex, and of the redox changes of cytochromes and reaction center, were similar (± 15%) in both WT and B187DN chromatophores. DCCD effectively inhibited phase III of the carotenoid bandshift in both B187DN and WT chromatophores. The dependence of the kinetics and amplitude of phase III of the electrochromic shift on DCCD concentration was identical in WT and B187DN chromatophores, indicating that covalent modification of AspB187is not specifically responsible for the effect of DCCD-induced effects of cytochromebc1complex. Furthermore, no evidence for differential inhibition of electrogenesis and electron transport was found in either strain. We conclude that AspB187plays no crucial role in the protonogenic reactions ofbc1complex, since its replacement by asparagine does not lead to any significant effects on either the electrogenic reactions ofbc1complex, as revealed by phase III of the electrochromic shift of carotenoids, or sensitivity of turnover to DCCD.