Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
School of Energy Science and Engineering, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India; P.K. Sinha Centre for Bioenergy and Renewables, Indian Institute of Technology Kharagpur, Kharagpur, 721302, India.
Biochem Biophys Res Commun. 2022 Sep 17;621:14-19. doi: 10.1016/j.bbrc.2022.06.087. Epub 2022 Jul 3.
The complex cellular envelope is one of the major reasons behind the survival in hostile conditions and the emergence of the drug-resisting properties of mycobacteria. Phosphatidyl-myo-inositol hexamannoside (PIM), Lipomannan (LM), and Lipoarabinomannan (LAM) are important structural constituents of the cell envelope and have roles in modulating host immune functions. Phosphatidyl-myo-inositol (PI) is first mannosylated at the 2-position of the inositol group by phosphatidyl-myo-inositol mannosyltransferase A (PimA) to produce phosphatidyl-myo-inositol monomannoside (PIM). This PIM is then further mannosylated at the 6-position of the inositol group by phosphatidyl-myo-inositol mannosyltransferase B' (PimB') utilizing GDP-mannose as the mannose-donor to synthesize phosphatidyl-myo-inositol dimannoside (PIM) and GDP. Further mannosylation and acylation on PIM produce AcPIM, which can then be converted to either AcPIM or LM/LAM. Detailed functional mechanism of how PimB' transfers the mannose sugar to PIM is not understood. Using molecular docking, the interactions of PimB' with the substrate PIM and the product PIM are analyzed here. Molecular dynamics (MD) simulations of PimB' with the substrates and the products were performed for 300ns to find out critical residues involved in the mannose-transfer reaction. Docking and MD analyses indicated the residues R206 and R210 bind both PIM and PIM and are critical in the mannose-transfer reaction. The residues HEVGWSMLPGS and RTRGGGL were involved in the transfer of PIM from the active site. The residues IGG, K211, E290, G291, IV, and E298 were also important in the mannosylation reaction. The crucial residues obtained from this study may help design novel drugs against mycobacterial PimB'.
复杂的细胞包膜是分枝杆菌在恶劣环境中生存和产生耐药性的主要原因之一。磷酸甘露糖肌醇六甘露糖 (PIM)、脂阿拉伯甘露聚糖 (LAM) 和脂甘露聚糖 (LM) 是细胞包膜的重要结构成分，在调节宿主免疫功能方面发挥作用。磷酸肌醇首先在肌醇基团的 2 位被磷酸肌醇甘露糖基转移酶 A (PimA) 甘露糖化，生成磷酸肌醇单甘露糖 (PIM)。然后，磷酸肌醇甘露糖基转移酶 B' (PimB') 利用 GDP-甘露糖作为供体，在肌醇基团的 6 位进一步甘露糖化，合成磷酸肌醇二甘露糖 (PIM) 和 GDP。在 PIM 上进一步甘露糖化和酰化生成 AcPIM，然后 AcPIM 可转化为 AcPIM 或 LM/LAM。PimB' 将甘露糖糖转移到 PIM 的详细功能机制尚不清楚。本文使用分子对接分析了 PimB'与底物 PIM 和产物 PIM 的相互作用。对 PimB'与底物和产物进行了 300ns 的分子动力学 (MD) 模拟，以找出参与甘露糖转移反应的关键残基。对接和 MD 分析表明，残基 R206 和 R210 结合 PIM 和 PIM，在甘露糖转移反应中起关键作用。残基 HEVGWSMLPGS 和 RTRGGGL 参与 PIM 从活性部位的转移。残基 IGG、K211、E290、G291、IV 和 E298 也在甘露糖化反应中起重要作用。本研究获得的关键残基可能有助于设计针对分枝杆菌 PimB' 的新型药物。
