Zannoni D, Melandri B A, Baccarini-Melandri A
Biochim Biophys Acta. 1976 Mar 12;423(3):413-30. doi: 10.1016/0005-2728(76)90197-3.
The respiratory chain of Rhodopseudomonas capsulata, strain St. Louis and of two respiration deficient mutants (M6 and M7) has been investigated by examining the redox and spectral characteristics of the cytochromes and their response to substrates and to specific respiratory inhibitors. Since the specific lesions of M6 and M7 have been localized on two different branches of the multiple oxidase system of the wild type strain, the capability for aerobic growth of these mutants can be considered as a proof of the physiological significance of both branched systems "in vivo". Using M6 and M7 mutants the response of the branched chain to respiratory inhibitors could be established. Cytochrome oxidase activity, a specific function of an high potential cytochrome b (E'0 = +413 mV) is sensitive to low concentrations of KCN (5-10(-5) M); CO is a specific inhibitor of an alternative oxidase, which is also inhibited by high concentrations of KCN (10(-3) M). Antimycin A inhibits preferentially the branch of the chain affected by low concentrations of cyanide. Redox titrations and spectral data indicate the presence in the membrane of three cytochromes of b type (E'0 = +413, +260, +47 vM) and two cytochromes of c type (E'0 = +342, +94 mV). A clear indication of the involvement in respiration of cytochrome b413, cytochrome c342 and cytochrome b47 has been obtained. Only 50% of the dithionite reducible cytochrome b can be reduced by respiratory substrates also in the presence of high concentrations of KCN or in anaerobiosis. The presence and function of quinones in the respiratory electron transport system has been clearly demonstrated. Quinones, which are reducible by NADH and succinate to about the same extent can be reoxidized through both branches of the respiratory chain, as shown by the response of their redox state to KCN. The possible site of the branching of the electron transport chain has been investigated comparing the per cent level of reduction of quinones and of cytochromes b and c as a function of KCN concentrations in membranes from wild type and M6 mutants cells. The site of the branching has been localized at the level of quinones-cytochrome b47. A tentative scheme of the respiratory chains operating in Rhodopseudomonas capsulata, St. Louis and in the two respiration deficient mutants, M6 and M7 is presented.
通过检测细胞色素的氧化还原和光谱特性及其对底物和特定呼吸抑制剂的反应，对荚膜红假单胞菌圣路易斯菌株以及两个呼吸缺陷突变体（M6和M7）的呼吸链进行了研究。由于M6和M7的特定损伤已定位在野生型菌株多氧化酶系统的两个不同分支上，这些突变体的有氧生长能力可被视为这两个分支系统在“体内”生理意义的证据。利用M6和M7突变体，可以确定分支链对呼吸抑制剂的反应。细胞色素氧化酶活性是一种高电位细胞色素b（E'0 = +413 mV）的特定功能，对低浓度的KCN（5-10^(-5) M）敏感；CO是交替氧化酶的特异性抑制剂，高浓度的KCN（10^(-3) M）也可抑制该酶。抗霉素A优先抑制受低浓度氰化物影响的呼吸链分支。氧化还原滴定和光谱数据表明，膜中存在三种b型细胞色素（E'0 = +413、+260、+47 vM）和两种c型细胞色素（E'0 = +342、+94 mV）。已明确获得细胞色素b413、细胞色素c342和细胞色素b47参与呼吸作用的证据。即使在高浓度KCN存在或厌氧条件下，呼吸底物也只能还原50%的连二亚硫酸盐可还原型细胞色素b。呼吸电子传递系统中醌的存在和功能已得到明确证明。醌可被NADH和琥珀酸以大致相同的程度还原，并可通过呼吸链的两个分支再氧化，这从其氧化还原状态对KCN的反应中可以看出。通过比较野生型和M6突变体细胞膜中醌以及细胞色素b和c的还原百分比水平随KCN浓度的变化，研究了电子传递链分支的可能位点。分支位点已定位在醌-细胞色素b47水平。本文给出了荚膜红假单胞菌圣路易斯菌株以及两个呼吸缺陷突变体M6和M7中运行的呼吸链的初步示意图。
