Endogenous H2O2 produced by Streptococcus pneumoniae controls FabF activity
Endogenous H2O2 produced by Streptococcus pneumoniae controls FabF activity
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DOI：
10.1016/j.bbalip.2010.06.004
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发表时间：
2010-09-01
影响因子：
4.8
通讯作者：
Porat, Nurith
中科院分区：
文献类型：
--
作者：
Benisty, Rachel;Cohen, Aharon Yehonatan;Porat, Nurith
FabF延伸缩合酶是决定FASII途径产生的产物谱的关键因素。其活性位点含有一个关键的半胱氨酸-巯基残基，这是一个合理的目标氧化H2 O2。肺炎链球菌产生异常高水平的H2 O2，主要通过丙酮酸氧化酶（SpxB）将丙酮酸转化为乙酰-P。我们目前的证据表明，内源性H2 O2抑制FabF活性的特异性氧化其活性位点的半胱氨酸巯基残基。巯基捕获方法显示，野生型菌株中的三个FabF半胱氨酸之一被氧化，而在spxB突变体中，H2 O2产生缺陷，没有半胱氨酸被氧化，表明FabF氧化还原状态的差异源于内源性H2 O2。在体外暴露的spxB突变体的各种过氧化氢浓度进一步证实，只有一个半胱氨酸残基是容易氧化。通过阻断FabF活性位点半胱氨酸与浅蓝菌素，我们表明，氧化的半胱氨酸是催化的。H2 O2或浅蓝菌素抑制FabF活性会导致膜脂肪酸组成改变。结果表明，S.肺炎。(C)2010爱思唯尔有限公司版权所有。
FabF elongation condensing enzyme is a critical factor in determining the spectrum of products produced by the FASII pathway. Its active site contains a critical cysteine-thiol residue, which is a plausible target for oxidation by H2O2. Streptococcus pneumoniae produces exceptionally high levels of H2O2, mainly through the conversion of pyruvate to acetyl-P via pyruvate oxidase (SpxB). We present evidence showing that endogenous H2O2 inhibits FabF activity by specifically oxidizing its active site cysteine-thiol residue. Thiol trapping methods revealed that one of the three FabF cysteines in the wild-type strain was oxidized, whereas in an spxB mutant, defective in H2O2 production, none of the cysteines was oxidized, indicating that the difference in FabF redox state originated from endogenous H2O2. In vitro exposure of the spxB mutant to various H2O2 concentrations further confirmed that only one cysteine residue was susceptible to oxidation. By blocking FabF active site cysteine with cerulenin we show that the oxidized cysteine was the catalytic one. Inhibition of FabF activity by either H2O2 or cerulenin resulted in altered membrane fatty acid composition. We conclude that FabF activity is inhibited by H2O2 produced by S. pneumoniae. (C) 2010 Elsevier B.V. All rights reserved.