ENZYMES OF AMINO ACID BIOSYNTHESIS

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。 结核分枝杆菌利用硫转移蛋白机制，在巨噬细胞吞噬氧化应激环境时，生物合成半胱氨酸。该系统涉及蛋白质Rv1335(Cys0)和Rv1336(CysM)。在结核分枝杆菌中存在半胱氨酸的替代途径，但使用硫化物作为硫源，当暴露在氧化剂中时，硫化物很容易被氧化成硫酸盐。结核分枝杆菌已经进化出利用泛素样蛋白作为硫转移蛋白Cyso的能力，通过产生活性较低的硫代羧基C末端作为硫源。CysO能够通过其灵活的二环基C-末端将硫原子传递到CysM的活性部位，CysM是一种利用b-消除酶的5‘-磷酸吡哆醇。在古生代，负责芳香氨基酸生物合成的前两步导致3-脱氢奎尼酸(DHQ)的同源基因缺失。最近，简氏甲烷球菌的两种蛋白产物Mj0400和Mj1249被报道为DHQ形成的非同源催化剂。这些酶的晶体结构有助于底物的鉴定和催化机理的阐明。已经解决了结构问题，发表了论文。

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. Mycobacterium tuberculosis utilizes a sulfur transfer protein mechanism to biosynthesize cysteine when exposed to the oxidative stress environment upon phagocytosis by a macrophage. This system involves the proteins Rv1335 (CysO) and Rv1336 (CysM). An alternative pathway to cysteine in M. tuberculosis exists, but uses sulfide as the sulfur source, which is readily oxidized to sulfate when exposed to oxidizing agents. M. tuberculosis has evolved the ability to utilize a ubiquitin like protein as a sulfur transfer protein, CysO, to serve as the sulfur source by generating a less reactive thio-caryboxy C-terminus. CysO is able to deliver the sulfur atom through its flexible digylcyl C-terminus into the active site of CysM, which is a pyridoxyl 5'-phosphate utilizing b-elimination enzyme. In Archaea, orthologous genes responsible for the first two steps of the aromatic amino acid biosynthesis leading to 3-dehydroquinate (DHQ) are missing. Recently, two protein products from Methanocaldococcus jannaschii, Mj0400 and Mj1249, have been reported as the nonorthologous catalysts of the DHQ formation. Crystal structures of these enzymes assisted the identification of the substrates and the elucidation of their catalytic mechanisms. Structures have been solved and papers published.