FREE METHIONINE-(R)-SULFOXIDE REDUCTASE 2

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 甲硫氨酸亚砜(MetO)的还原是由甲硫氨酸亚砜还原酶(MSR)介导的。MSRA和MSRB家族可以在多肽或蛋白质环境中减少游离的Meto和Meto。这一过程是立体特异性的，MSRA和MSRB分别修复了S和R型的Meto。相反，fRMsr是一种细菌酶，专用于游离形式的Met-(R)-O。E.colifRMsr是第一个表现出酶活性的GAF结构域家族成员(Lin等人)。2007 PNAS 104：9597)。其他GAF结构域蛋白取代半胱氨酸残基和其他残基，与环核苷酸、生色团和许多其他配体特异性结合，进行信号增强。因此，在某些生物体中，Met-(R)-O可能是一种通过TOR途径响应氧化应激和营养的信号分子。此外，fRMsr可能在维持细菌中减少的Met蛋白质合成池中发挥关键作用。FRMsr酶是药物设计的一个有吸引力的目标，因为人类不拥有这种蛋白质。定点突变和动力学分析表明，三个半胱氨酸残基参与了fRMsr的催化机制，其中包括一个半胱氨酸磺酸中间体。虽然其机制似乎类似于其他MSR酶，但识别底物的结构基础是新的。此外，两个半胱氨酸残基位于表面环上，当MetO还原时，这些环导致形成二硫键(Cys84-Cys118)并完全封闭活性中心空腔。目前的努力已经导致了甲硫氨酸产物络合物的结晶学测定。在这个杂岩中，活动位点环显示出明显的结构重排。这项研究的重点是确定Cys94-Cys118反应中间体，它应该显示出更戏剧性的结构重排。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. 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. In contrast, fRMsr is a bacterial enzyme specific for the free form of Met-(R)-O. E. coli fRMsr is the first GAF domain family member to show enzymatic activity (Lin et al. 2007 PNAS 104:9597). 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. Moreover, fRMsr may play a key role in maintaining the reduced Met pool for protein synthesis in bacteria. The fRMsr enzyme is an attractive target for drug design as humans do not possess this protein. Site-directed mutagenesis and kinetic analyses have shown that three Cys residues are involved in the fRMsr catalytic mechanism, including a Cys sulfenic acid intermediate. While the mechanism appears to be similar to the other Msr enzymes, the structural basis for the recognition of the substrate is novel. Moreover, two of the Cys residues are located on surface loops that upon MetO reduction result in the formation of a disulfide bond (Cys84-Cys118) and complete enclosure of the active site cavity. Current efforts have lead to the crystallographic determination of the Met product complex. In this complex the active site loops show marked structural rearrangement. The focus of this study is to determine the Cys94-Cys118 reaction intermediate, which should show even more dramatic structural rearrangements.