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首页> 外文期刊>Journal of Molecular Biology >Peptidoglycan remodeling in Mycobacterium tuberculosis: comparison of structures and catalytic activities of RipA and RipB.
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Peptidoglycan remodeling in Mycobacterium tuberculosis: comparison of structures and catalytic activities of RipA and RipB.

机译：结核分枝杆菌中的肽聚糖重塑：RipA和RipB的结构和催化活性的比较。

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摘要

The success of Mycobacterium tuberculosis in sustaining long-term survival within the host macrophages partly relies on its unique cell envelop that also confers low susceptibility to several antibiotics. Remodeling of the septal peptidoglycan (PG) has been linked to the putative PG hydrolases RipA and RipB. The crystal structures of RipB (Rv1478) and the homologous module of RipA (Rv1477) were determined to 1.60 A and 1.38 A resolution, respectively. Both proteins contain a C-terminal core domain resembling the NlpC-type PG hydrolases. However, the structure of RipB exhibits striking differences to the structures of this domain in RipA reported here and previously by others. Major structural differences were found in the N-terminal segments of 70 amino acids and in an adjacent loop, which form part of the substrate binding groove. Both RipA and RipB are able to bind PG. RipA, its C-terminal module and RipB cleave defined PG fragments between d-glutamate and meso-diaminopimelate with pH optima of 5 and 6, respectively. The peptidase module of RipA is also able to degrade Bacillus subtilis PG, which displays peptide stems and cross-links identical with those found in mycobacterial murein. RipB did not show comparable hydrolase activity with this substrate. Removal of the N-terminal segments previously suggested to have a role in auto-inhibition did not change the activity of either RipA or RipB. A comparison of the putative active-site clefts in the two enzymes provides structural insights into the basis of the differences in their substrate specificity.
机译：结核分枝杆菌在维持宿主巨噬细胞内长期存活方面的成功部分取决于其独特的细胞包膜，这种包膜还赋予了对几种抗生素的低敏感性。间隔肽聚糖（PG）的重塑已与推定的PG水解酶RipA和RipB相关联。确定RipB（Rv1478）的晶体结构和RipA（Rv1477）的同源模块的分辨率分别为1.60 A和1.38A。两种蛋白质都包含一个类似于NlpC型PG水解酶的C末端核心结构域。然而，RipB的结构与此处和其他人先前报道的RipA中此域的结构表现出显着差异。在70个氨基酸的N末端片段和相邻的环中发现了主要的结构差异，这些环形成了底物结合槽的一部分。 RipA和RipB都可以绑定PG。 RipA，其C端模块和RipB分别在d-谷氨酸和内消旋二氨基庚二酸酯之间定义了PG片段，最适pH分别为5和6。 RipA的肽酶模块还能够降解枯草芽孢杆菌PG，该菌株显示出与分枝杆菌Murein中相同的肽茎和交联。 RipB没有显示与此底物相当的水解酶活性。以前建议在自动抑制中起作用的N末端片段的去除不会改变RipA或RipB的活性。两种酶中假定的活性位点裂隙的比较为了解其底物特异性差异的基础提供了结构上的见解。

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