Lorence R M, Green G N, Gennis R B
J Bacteriol. 1984 Jan;157(1):115-21. doi: 10.1128/jb.157.1.115-121.1984.
A combination of potentiometric analysis and electrochemically poised low-temperature difference spectroscopy was used to examine a mutant strain of Escherichia coli that was previously shown by immunological criteria to be lacking the cytochrome d terminal oxidase. It was shown that this strain is missing cytochromes d, a1, and b558 and that the cytochrome composition of the mutant is similar to that of the wild-type strain grown under conditions of high aeration. The data indicate that the high-aeration branch of the respiratory chain contains two cytochrome components, b556 (midpoint potential [Em] = +35 mV) and cytochrome o (Em = +165 mV). The latter component binds to CO and apparently has a reduced-minus-oxidized split-alpha band with peaks at 555 and 562 nm. When the wild-type strain was grown under conditions of low aeration, the components of the cytochrome d terminal oxidase complex were observed: cytochrome d (Em = +260 mV), cytochrome a1 (Em = +150 mV) and cytochrome b558 (Em = +180 mV). All cytochromes appeared to undergo simple one-electron oxidation-reduction reactions. In the absence of CO, cytochromes b558 and o have nearly the same Em values. In the presence of CO, the Em of cytochrome o is raised, thus allowing cytochromes b558 and o to be individually quantitated by potentiometric analysis when they are both present.
采用电位分析和电化学平衡低温差光谱相结合的方法，对一株大肠杆菌突变株进行了检测。此前通过免疫学标准已证明该突变株缺乏细胞色素d末端氧化酶。结果表明，该菌株缺失细胞色素d、a1和b558，且突变株的细胞色素组成与在高通气条件下生长的野生型菌株相似。数据表明，呼吸链的高通气分支包含两种细胞色素成分，即b556（中点电位[Em]=+35 mV）和细胞色素o（Em=+165 mV）。后一种成分与CO结合，显然具有还原态减去氧化态的分裂α带，其峰值分别位于555和562 nm处。当野生型菌株在低通气条件下生长时，可观察到细胞色素d末端氧化酶复合物的成分：细胞色素d（Em=+260 mV）、细胞色素a1（Em=+150 mV）和细胞色素b558（Em=+180 mV）。所有细胞色素似乎都经历简单的单电子氧化还原反应。在没有CO的情况下，细胞色素b558和o的Em值几乎相同。在有CO的情况下，细胞色素o的Em升高，因此当细胞色素b558和o同时存在时，可通过电位分析对它们进行单独定量。
