Free methionine-(R)-sulfoxide reductase from Escherichia coli reveals a new GAF domain function
Free methionine-(R)-sulfoxide reductase from Escherichia coli reveals a new GAF domain function
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DOI：
10.1073/pnas.0703774104
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发表时间：
2007-06-05
影响因子：
11.1
通讯作者：
Lowther, W. Todd
中科院分区：
文献类型：
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作者：
Lin, Zhidong;Johnson, Lynnette C.;Lowther, W. Todd
蛋氨酸亚砜（MetO）的还原是由蛋氨酸亚砜还原酶（Msr）介导。MsrA和MsrB家族可以在肽或蛋白质环境中减少游离MetO和MetO。这个过程是立体特异性的，分别由MsrA和MsrB修复的S-和r -形式的MetO。从MsrA(-)B（-）敲除的大肠杆菌中提取的细胞提取物具有几种剩余的Msr活性。本研究通过蛋白质组学分析确定了一种针对游离形式Met-(R)- o的特异性酶fRMsr。重组酶具有与MsrA家族成员相同的底物特异性和活性。然而，大肠杆菌fRMsr酶对游离Met-(R)- o的活性比不含硒半胱氨酸的MsrB酶高100到1000倍。大肠杆菌fRMsr的晶体结构先前已被确定，但没有已知的功能。因此，这种蛋白质的功能现在已经确定。大肠杆菌和酵母蛋白的结构相似性表明，大多数fRMsrs使用三个半胱氨酸残基进行催化和形成二硫键来包裹一个小的活性位点空腔。后一种特征很可能是底物特异性的关键决定因素。此外，大肠杆菌fRMsr是第一个显示酶活性的GAF结构域家族成员。其他GAF结构域蛋白替代Cys残基和其他蛋白特异性结合环核苷酸、发色团和许多其他配体来增强信号。因此，Met-(R)- o可能是一些生物体通过TOR途径响应氧化应激和营养物质的信号分子。
The reduction of methionine sulfoxide (MetO) is mediated by methionine sulfoxide reductases (Msr). The MsrA and MsrB families can reduce free MetO and MetO within a peptide or protein context. This process is stereospecific with the S- and R-forms of MetO repaired by MsrA and MsrB, respectively. Cell extracts from an MsrA(-)B(-) knockout of Escherichia coli have several remaining Msr activities. This study has identified an enzyme specific for the free form of Met-(R)-O, fRMsr, through proteomic analysis. The recombinant enzyme exhibits the same substrate specificity and is as active as MsrA family members. E. coli fRMsr is, however, 100- to 1,000-fold more active than non-selenocysteine-containing MsrB enzymes for free Met-(R)-O. The crystal structure of E. coli fRMsr was previously determined, but no known function was assigned. Thus, the function of this protein has now been determined. The structural similarity of the E. coli and yeast proteins suggests that most fRMsrs use three cysteine residues for catalysis and the formation of a disulfide bond to enclose a small active site cavity. This latter feature is most likely a key determinant of substrate specificity. Moreover, E. coli fRMsr is the first GAF domain family member to show enzymatic activity. Other GAF domain proteins substitute the Cys residues and others to specifically bind cyclic nucleotides, chromophores, and many other ligands for signal potentiation. Therefore, Met-(R)-O may represent a signaling molecule in response to oxidative stress and nutrients via the TOR pathway in some organisms.