Pandey Bharati, Grover Sonam, Tyagi Chetna, Goyal Sukriti, Jamal Salma, Singh Aditi, Kaur Jagdeep, Grover Abhinav
Department of Biotechnology, Panjab University, Chandigarh 160014, India.
Kusuma School of Biological Sciences, Indian Institute of Technology Delhi, New Delhi 110016, India.
Gene. 2016 Apr 25;581(1):31-42. doi: 10.1016/j.gene.2016.01.024. Epub 2016 Jan 16.
The latest resurrection of drug resistance poses serious threat to the treatment and control of the disease. Mutations have been detected in panD gene in the Mycobacterium tuberculosis (Mtb) strains. Mutation of histidine to arginine at residue 21 (H21R) and isoleucine to valine at residue 29 (I49V) in the non-active site of panD gene has led to PZA resistance. This study will help in reconnoitering the mechanism of pyrazinamide (PZA) resistance caused due to double mutation identified in the panD gene of M. tuberculosis clinical isolates. It is known that panD gene encodes aspartate decarboxylase essential for β-alanine synthesis that makes it a potential therapeutic drug target for tuberculosis treatment. The knowledge about the molecular mechanism conferring drug resistance in M. tuberculosis is scarce, which is a significant challenge in designing successful therapeutic drug. In this study, structural and dynamic repercussions of H21R-I49V double mutation in panD complexed with PZA have been corroborated through docking and molecular dynamics based simulation. The double mutant (DM) shows low docking score and thus, low binding affinity for PZA as compared to the native protein. It was observed that the mutant protein exhibits more structural fluctuation at the ligand binding site in comparison to the native type. Furthermore, the flexibility and compactness analyses indicate that the double mutation influence interaction of PZA with the protein. The hydrogen-bond interaction patterns further supported our results. The covariance and PCA analysis elucidated that the double mutation affects the collective motion of residues in phase space. The results have been presented with an explanation for the induced drug resistance conferred by the H21R-I49V double mutation in panD gene and gain valuable insight to facilitate the advent of efficient therapeutics for combating resistance against PZA.
耐药性的最新复苏对该疾病的治疗和控制构成了严重威胁。在结核分枝杆菌（Mtb）菌株的panD基因中检测到了突变。panD基因非活性位点上第21位残基的组氨酸突变为精氨酸（H21R）以及第29位残基的异亮氨酸突变为缬氨酸（I49V）导致了对吡嗪酰胺（PZA）的耐药性。本研究将有助于探究由于在结核分枝杆菌临床分离株的panD基因中鉴定出的双突变而导致的吡嗪酰胺（PZA）耐药机制。已知panD基因编码对β-丙氨酸合成至关重要的天冬氨酸脱羧酶，这使其成为结核病治疗的潜在治疗药物靶点。关于结核分枝杆菌中赋予耐药性的分子机制的知识匮乏，这是设计成功治疗药物的一项重大挑战。在本研究中，通过对接和基于分子动力学的模拟，证实了与PZA复合的panD中H21R-I49V双突变的结构和动力学影响。与天然蛋白相比，双突变体（DM）显示出较低的对接分数，因此对PZA的结合亲和力较低。观察到与天然类型相比，突变蛋白在配体结合位点表现出更多的结构波动。此外，灵活性和紧凑性分析表明双突变影响PZA与蛋白质的相互作用。氢键相互作用模式进一步支持了我们的结果。协方差和主成分分析阐明双突变影响相空间中残基的集体运动。研究结果对panD基因中H21R-I49V双突变诱导的耐药性进行了解释，并为促进对抗PZA耐药性的高效治疗方法的出现提供了有价值的见解。
