Cytochrome bd oxidase, oxidative stress, and dioxygen tolerance of the strictly anaerobic bacterium Moorella thermoacetica
Cytochrome bd oxidase, oxidative stress, and dioxygen tolerance of the strictly anaerobic bacterium Moorella thermoacetica
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DOI：
10.1128/jb.187.6.2020-2029.2005
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发表时间：
2005-03-01
影响因子：
3.2
通讯作者：
Kurtz, DM
中科院分区：
文献类型：
--
作者：
Das, A;Silaghi-Dumitrescu, R;Kurtz, DM
革兰氏阳性、嗜热、产乙酸细菌Moorella thermoacetica可以通过Wood-Ljungdahl（乙酰辅酶A合成）途径将CO2还原为乙酸。本报告表明，尽管M.热乙酸酶含有膜结合的细胞色素BD氧化酶，其可以催化低水平的分子氧的还原。M. thermoacetica具有显着的内源O-2摄取活性，并且该活性在甲醇或CO存在下增加，甲醇或CO是Wood-Ljungdahl途径中的底物。氰化物和叠氮化物强烈（类似于70%）抑制内源性和CO/甲醇依赖的O-2吸收。研究了木霉正十二烷基-β-麦芽糖苷提取物的紫外-可见光吸收光谱和电子顺磁共振谱。热醋酸菌膜显示存在含有细胞色素B（561）、细胞色素B（595）和细胞色素d（二氢卟酚）的细胞色素bd氧化酶复合物。通过N-末端氨基酸测序鉴定了bd氧化酶的亚基I和II。分枝热乙酸菌细胞色素BD氧化酶表现出氰化物敏感的醌醇氧化酶活性。分枝热醋酸菌细胞色素bd（cyd）操纵子由四个基因组成，编码亚基I和II以及两个ABC型转运蛋白，其在其他细菌中的同源物是组装bd复合物所必需的。当M.在不存在添加的还原剂（半胱氨酸+H，S）的情况下生长热乙酸菌。一个35 kDa的胞质蛋白，确定为半胱氨酸合酶（CysK）的表达，也诱导了非还原生长条件。综合证据表明，细胞色素bd氧化酶和半胱氨酸合酶保护免受氧化应激，并有助于M.热醋酸。
The gram-positive, thermophillic, acetogenic bacterium Moorella thermoacetica can reduce CO2 to acetate via the Wood-Ljungdahl (acetyl coenzyme A synthesis) pathway. This report demonstrates that, despite its classification as a strict anaerobe, M. thermoacetica contains a membrane-bound cytochrome bd oxidase that can catalyze reduction of low levels of dioxygen. Whole-cell suspensions of M. thermoacetica had significant endogenous O-2 uptake activity, and this activity was increased in the presence of methanol or CO, which are substrates in the Wood-Ljungdahl pathway. Cyanide and azide strongly (similar to 70%) inhibited both the endogenous and CO/methanol-dependent O-2 uptake. UV-visible light absorption and electron paramagnetic resonance spectra of n-dodecyl-beta-maltoside extracts of M. thermoacetica membranes showed the presence of a cytochrome bd oxidase complex containing cytochrome b(561), cytochrome b(595), and cytochrome d (chlorin). Subunits I and II of the bd oxidase were identified by N-terminal amino acid sequencing. The M. thermoacetica cytochrome bd oxidase exhibited cyanide-sensitive quinol oxidase activity. The M. thermoacetica cytochrome bd (cyd) operon consists of four genes, encoding subunits I and Il along with two ABC-type transporter proteins, homologs of which in other bacteria are required for assembly of the bd complex. The level of this cyd operon transcript was significantly increased when M. thermoacetica was grown in the absence of added reducing agent (cysteine + H,S). Expression of a 35-kDa cytosolic protein, identified as a cysteine synthase (CysK), was also induced by the nonreducing growth conditions. The combined evidence indicates that cytochrome bd oxidase and cysteine synthase protect against oxidative stress and contribute to the limited dioxygen tolerance of M. thermoacetica.