Structure of LdtMt2, an L,D-transpeptidase from Mycobacterium tuberculosis
Structure of LdtMt2, an L,D-transpeptidase from Mycobacterium tuberculosis
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DOI：
10.1107/s0907444912049268
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发表时间：
2013-03-01
期刊：
影响因子：
--
通讯作者：
Schneider, Gunter
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作者：
Both, Dominic;Steiner, Eva Maria;Schneider, Gunter
转肽酶 LtdMt2 催化结核分枝杆菌细胞壁中肽聚糖层的 (33) 交联特征的形成。生物信息学分析表明，该酶的膜外部分由三个结构域组成：两个较小的结构域（表示为 A 和 B 结构域）和位于 C 末端的转肽酶结构域（C 结构域）。包含AB域和BC域的两个片段的晶体结构已被确定。 BC 模块的结构使用 Se-SAD 定相确定为 1.86 埃分辨率，由具有免疫球蛋白相关折叠的 B 结构域和属于 ErfK/YbiS/YbnG 折叠家族的催化结构域组成。 AB 结构域片段的结构通过分子替换解析至 1.45 埃分辨率，表明尽管缺乏整体序列同一性，但 A 结构域在结构上与 B 结构域非常相似。结合两个片段的结构提供了 LdtMt2 完整的三结构域膜外部分的视图，并显示该蛋白质从质膜延伸到肽聚糖层至少 80100 埃，从而定义了该酶形成交联的最大距离。 LdtMt 相关转肽酶含有一个或两个免疫球蛋白结构域，这表明它们可能作为延伸单元，将催化结构域定位在距肽聚糖层膜适当的距离处。
The transpeptidase LtdMt2 catalyzes the formation of the (33) cross-links characteristic of the peptidoglycan layer in the Mycobacterium tuberculosis cell wall. Bioinformatics analysis suggests that the extramembrane part of the enzyme consists of three domains: two smaller domains (denoted as A and B domains) and a transpeptidase domain (the C domain) at the C-terminus. The crystal structures of two fragments comprising the AB domains and the BC domains have been determined. The structure of the BC module, which was determined to 1.86 angstrom resolution using Se-SAD phasing, consists of the B domain with an immunoglobulin-related fold and the catalytic domain belonging to the ErfK/YbiS/YbnG fold family. The structure of the AB-domain fragment, which was solved by molecular replacement to 1.45 angstrom resolution, reveals that despite a lack of overall sequence identity the A domain is structurally very similar to the B domain. Combining the structures of the two fragments provides a view of the complete three-domain extramembrane part of LdtMt2 and shows that the protein extends at least 80100 angstrom from the plasma membrane into the peptidoglycan layer and thus defines the maximal distance at which cross-links are formed by this enzyme. The LdtMt-related transpeptidases contain one or two immunoglobulin domains, which suggests that these might serve as extender units to position the catalytic domain at an appropriate distance from the membrane in the peptidoglycan layer.