Structure and Inhibitor Specificity of L,D-Transpeptidase (LdtMt2) from Mycobacterium tuberculosis and Antibiotic Resistance: Calcium Binding Promotes Dimer Formation
Structure and Inhibitor Specificity of L,D-Transpeptidase (LdtMt2) from Mycobacterium tuberculosis and Antibiotic Resistance: Calcium Binding Promotes Dimer Formation
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DOI：
10.1208/s12248-018-0193-x
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发表时间：
2018-03-01
期刊：
影响因子：
4.5
通讯作者：
Varughese, Kottayil I.
中科院分区：
文献类型：
--
作者：
Gokulan, Kuppan;Khare, Sangeeta;Varughese, Kottayil I.
所有细菌中肽聚糖（PG）合成的最后一步是PG茎之间交联的形成。不同PG链中的氨基酸之间的交联赋予肽聚糖细胞壁三维结构，并为其增加强度和刚度。细菌细胞壁中有两种不同类型的交联。D，D-转肽酶（D，D-TP）产生经典的4 -> 3交联，L，D-转肽酶（L，D-TP）产生3 -> 3非经典的肽交联。本研究旨在了解与L，D-TP相关的耐药性的本质，并为设计针对多重耐药细菌的新型抗生素提供见解。青霉素和头孢菌素类β-内酰胺类不能抑制L，D-TP功能;然而，碳青霉烯类抑制其功能。我们分析了结核分枝杆菌L，D-TP在载脂蛋白形式和与美罗培南和亚胺培南复合物中的结构。L，D-TP的周质区折叠成三个结构域。催化残基位于C末端结构域中。酰化反应发生在碳青霉烯抗生素和催化Cys-354之间，形成共价复合物。该加合物形成模拟L，D-TP与供体PG-茎的酰化。这项研究的一个新的方面是，在载脂蛋白和碳青霉烯复合物的晶体结构中，N-末端结构域有一个非共价键合到它的muropeptide单元。另一个有趣的观察是，钙复合物结晶为二聚体通过头部和尾部单体之间的相互作用。
The final step of peptidoglycan (PG) synthesis in all bacteria is the formation of cross-linkage between PG-stems. The cross-linking between amino acids in different PG chains gives the peptidoglycan cell wall a 3-dimensional structure and adds strength and rigidity to it. There are two distinct types of cross-linkages in bacterial cell walls. D, D-transpeptidase (D, D-TPs) generate the classical 4 -> 3 cross-linkages and the L, D-transpeptidase (L, D-TPs) generate the 3 -> 3 non-classical peptide cross-linkages. The present study is aimed at understanding the nature of drug resistance associated with L, D-TP and gaining insights for designing novel antibiotics against multi-drug resistant bacteria. Penicillin and cephalosporin classes of beta-lactams cannot inhibit L, D-TP function; however, carbapenems inactivate its function. We analyzed the structure of L, D-TP of Mycobacterium tuberculosis in the apo form and in complex with meropenem and imipenem. The periplasmic region of L, D-TP folds into three domains. The catalytic residues are situated in the C-terminal domain. The acylation reaction occurs between carbapenem antibiotics and the catalytic Cys-354 forming a covalent complex. This adduct formation mimics the acylation of L, D-TP with the donor PG-stem. A novel aspect of this study is that in the crystal structures of the apo and the carbapenem complexes, the N-terminal domain has a muropeptide unit non-covalently bound to it. Another interesting observation is that the calcium complex crystallized as a dimer through head and tail interactions between the monomers.