Methionine sulfoxide reductase B3 requires resolving cysteine residues for full activity and can act as a stereospecific methionine oxidase.
Methionine sulfoxide reductase B3 requires resolving cysteine residues for full activity and can act as a stereospecific methionine oxidase.
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蛋氨酸亚氧化亚氧化物还原酶B3需要解决半胱氨酸残基以进行全活性，并且可以作为立体特异性蛋氨酸氧化酶。
DOI：
10.1042/bcj20170929
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发表时间：
2018-02-28
期刊：
影响因子：
--
通讯作者：
Bulleid NJ
中科院分区：
文献类型：
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作者：
Cao Z;Mitchell L;Hsia O;Scarpa M;Caldwell ST;Alfred AD;Gennaris A;Collet JF;Hartley RC;Bulleid NJ
蛋白质中蛋氨酸残基的氧化发生在氧化应激过程中，可导致蛋白质功能的改变。蛋氨酸亚砜还原酶（Msr）可以逆转这种修饰。在这里，我们描述了哺乳动物酶Msr B3。这种酶有两种剪接变体，它们的不同之处在于它们的n端信号序列，这将蛋白质引导到内质网（ER）或线粒体。我们在这里证明了该酶可以补充依赖于蛋氨酸亚砜还原生长的细菌菌株，纯化的重组蛋白具有酶活性，对r -蛋氨酸亚砜表现出立体特异性，并确定了活性位点和两个分解半胱氨酸残基。该酶仅在两种溶解半胱氨酸残基存在的情况下才能被硫氧还蛋白有效地再循环。这些结果表明，对于Msrs的这种同工异构体，还原周期最有可能通过三个步骤进行。这包括活性位点硫醇的初始磺化，随后形成具有溶解硫醇基团的链内二硫，并通过硫氧还蛋白样蛋白还原该二硫来完成，以再生活性位点硫醇。有趣的是，该酶还可以作为氧化酶催化r -蛋氨酸亚砜的立体特异性形成。这一结果对该酶在内质网和线粒体蛋白可逆修饰中的作用具有重要意义。
The oxidation of methionine residues in proteins occurs during oxidative stress and can lead to an alteration in protein function. The enzyme methionine sulfoxide reductase (Msr) reverses this modification. Here, we characterise the mammalian enzyme Msr B3. There are two splice variants of this enzyme that differ only in their N-terminal signal sequence, which directs the protein to either the endoplasmic reticulum (ER) or mitochondria. We demonstrate here that the enzyme can complement a bacterial strain, which is dependent on methionine sulfoxide reduction for growth, that the purified recombinant protein is enzymatically active showing stereospecificity towards R-methionine sulfoxide, and identify the active site and two resolving cysteine residues. The enzyme is efficiently recycled by thioredoxin only in the presence of both resolving cysteine residues. These results show that for this isoform of Msrs, the reduction cycle most likely proceeds through a three-step process. This involves an initial sulfenylation of the active site thiol followed by the formation of an intrachain disulfide with a resolving thiol group and completed by the reduction of this disulfide by a thioredoxin-like protein to regenerate the active site thiol. Interestingly, the enzyme can also act as an oxidase catalysing the stereospecific formation of R-methionine sulfoxide. This result has important implications for the role of this enzyme in the reversible modification of ER and mitochondrial proteins.