The crystal structure of M-leprae ML2640c defines a large family of putative S-adenosylmethionine-dependent methyltransferases in mycobacteria
The crystal structure of M-leprae ML2640c defines a large family of putative S-adenosylmethionine-dependent methyltransferases in mycobacteria
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DOI：
10.1110/ps.072982707
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发表时间：
2007-09-01
期刊：
影响因子：
8
通讯作者：
Alzari, Pedro M.
中科院分区：
文献类型：
--
作者：
Grana, Martin;Haouz, Ahmed;Alzari, Pedro M.
麻风分枝杆菌蛋白ML2640c属于一个保守的假设蛋白家族，主要存在于分枝杆菌中，其中一些可能是S-腺苷蛋氨酸(ADOMet)依赖性甲基转移酶(MTase)。作为结构基因组学关于致病分枝杆菌保守假设蛋白的一部分，我们已经确定了ML2640c的两种不同晶体形式的结构。正如预期的那样，ML2640c具有典型的MTase核心域，并以与该结构家族其他已知成员一致的方式与甲基供体底物ADOMet结合。ML2640c可能的受体底物结合部位是一个大的内腔，大部分排列着芳香族和脂肪族侧链残基，这表明类脂分子可能是催化的靶点。将结合部位从主体溶剂中分离出来并在晶体结构中具有高度移动性的翻盖片段(残基222-256)可以作为底物进入和产物释放的门户。ML2640c样蛋白的多个序列比对表明，该家族的中心α/β核心和ADOMet结合位点非常保守。然而，定义受体底物结合位置的氨基酸位置表现出较高的可变性，暗示着不同的受体底物特异性。ML2640c的晶体结构首次提供了对这一重要的分枝杆菌蛋白家族的结构一瞥，并为它们作为ADOMet依赖的甲基转移酶的功能分配提供了强有力的支持。
Mycobacterium leprae protein ML2640c belongs to a large family of conserved hypothetical proteins predominantly found in mycobacteria, some of them predicted as putative S-adenosylmethionine ( AdoMet)-dependent methyltransferases ( MTase). As part of a Structural Genomics initiative on conserved hypothetical proteins in pathogenic mycobacteria, we have determined the structure of ML2640c in two distinct crystal forms. As expected, ML2640c has a typical MTase core domain and binds the methyl donor substrate AdoMet in a manner consistent with other known members of this structural family. The putative acceptor substrate-binding site of ML2640c is a large internal cavity, mostly lined by aromatic and aliphatic side-chain residues, suggesting that a lipid-like molecule might be targeted for catalysis. A flap segment ( residues 222-256), which isolates the binding site from the bulk solvent and is highly mobile in the crystal structures, could serve as a gateway to allow substrate entry and product release. The multiple sequence alignment of ML2640c-like proteins revealed that the central alpha/beta core and the AdoMet-binding site are very well conserved within the family. However, the amino acid positions defining the binding site for the acceptor substrate display a higher variability, suggestive of distinct acceptor substrate specificities. The ML2640c crystal structures offer the first structural glimpses at this important family of mycobacterial proteins and lend strong support to their functional assignment as AdoMet-dependent methyltransferases.