Oxidative modification of protein structure has been shown to play a significant role in bacterial virulence and metabolism. The sulfur-containing residues are susceptible to oxidation and the enzymatic reversal of oxidized cysteine or methionine is detected in many organisms. Methionine sulfoxide reductases (Msr) are responsible for reducing oxidized methionine. The two different Msrs, MsrA and MsrB, reduce methionine R-sulfoxide and methionine S-sulfoxide, respectively through self-oxidation. This study elucidated the structure of MsrB from Staphylococcus aureus Mu50 and its changes upon oxidation. The active site shows two reduced cysteines in a close contact, implying disulfide bond would form without major structural rearrangement. When the protein is exposed to an oxidative condition, a dimeric state is observed. The dimerization of _SAMsrB creates a valley structure for accepting peptidyl substrates. To the best of our knowledge, oxidation induced dimerization of _SAMsrB would help to understand mechanism behind redox control that has not been well characterized.

已经显示蛋白质结构的氧化修饰在细菌毒力和代谢中起重要作用。含硫残基易于氧化，在许多生物中都检测到氧化半胱氨酸或蛋氨酸的酶促逆转。蛋氨酸亚砜还原酶（Msr）负责还原氧化的蛋氨酸。MsrA和MsrB这两种不同的Msrs通过自氧化分别还原甲硫氨酸R-亚砜和甲硫氨酸S-亚砜。这项研究阐明了金黄色葡萄球菌中MsrB的结构Mu50及其在氧化时的变化。活性位点显示两个紧密连接的半胱氨酸还原，这意味着二硫键将形成而没有主要的结构重排。当蛋白质暴露于氧化条件时，观察到二聚状态。_SA MsrB的二聚化形成了一个谷结构，用于接受肽基底物。据我们所知，氧化诱导的_SA MsrB的二聚化将有助于了解氧化还原控制背后的机制，该机制尚未得到很好的表征。