Rationally Designed Novel Phenyloxazoline Synthase Inhibitors: Chemical Synthesis and Biological Evaluation to Accelerate the Discovery of New Antimycobacterial Antibiotics
Mousumi Shyam,
Gourab Bhattacharje,
Chris Daniel,
Amrendra Kumar,
Pragya Yadav,
Piyali Mukherjee,
Samsher Singh,
Amit Kumar Das,
Tadigoppula Narender,
Amit Singh,
Venkatesan Jayaprakash,
Sanjib Bhakta
Affiliations
Mousumi Shyam
Department of Pharmaceutical Sciences & Technology, Birla Institute of Technology, Mesra, Ranchi 835215, India
Gourab Bhattacharje
Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
Chris Daniel
Mycobacteria Research Laboratory, School of Natural Sciences, Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
Amrendra Kumar
Division of Medicinal & Process Chemistry, CSIR-Central Drug Research Institute, Sector 10 Janakipuram Extension, Sitapur Road, Lucknow 226031, India
Pragya Yadav
Division of Medicinal & Process Chemistry, CSIR-Central Drug Research Institute, Sector 10 Janakipuram Extension, Sitapur Road, Lucknow 226031, India
Piyali Mukherjee
Department of Microbiology and Cell Biology, Centre for Infectious Disease Research, Indian Institute of Science, CV Raman Avenue, Bengaluru 560012, India
Samsher Singh
Department of Microbiology and Cell Biology, Centre for Infectious Disease Research, Indian Institute of Science, CV Raman Avenue, Bengaluru 560012, India
Amit Kumar Das
Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
Tadigoppula Narender
Division of Medicinal & Process Chemistry, CSIR-Central Drug Research Institute, Sector 10 Janakipuram Extension, Sitapur Road, Lucknow 226031, India
Amit Singh
Department of Microbiology and Cell Biology, Centre for Infectious Disease Research, Indian Institute of Science, CV Raman Avenue, Bengaluru 560012, India
Venkatesan Jayaprakash
Department of Pharmaceutical Sciences & Technology, Birla Institute of Technology, Mesra, Ranchi 835215, India
Sanjib Bhakta
Mycobacteria Research Laboratory, School of Natural Sciences, Institute of Structural and Molecular Biology, Birkbeck, University of London, Malet Street, London WC1E 7HX, UK
The uncontrolled spread of drug-resistant tuberculosis (DR-TB) clinical cases necessitates the urgent discovery of newer chemotypes with novel mechanisms of action. Here, we report the chemical synthesis of rationally designed novel transition-state analogues (TSAs) by targeting the cyclization (Cy) domain of phenyloxazoline synthase (MbtB), a key enzyme of the conditionally essential siderophore biosynthesis pathway. Following bio-assay-guided evaluation of TSA analogues preferentially in iron-deprived and iron-rich media to understand target preferentiality against a panel of pathogenic and non-pathogenic mycobacteria strains, we identified a hit, i.e., TSA-5. Molecular docking, dynamics, and MMPBSA calculations enabled us to comprehend TSA-5’s stable binding at the active site pocket of MbtB_Cy and the results imply that the MbtB_Cy binding pocket has a strong affinity for electron-withdrawing functional groups and contributes to stable polar interactions between enzyme and ligand. Furthermore, enhanced intracellular killing efficacy (8 μg/mL) of TSA-5 against Mycobacterium aurum in infected macrophages is noted in comparison to moderate in vitro antimycobacterial efficacy (64 μg/mL) against M. aurum. TSA-5 also demonstrates whole-cell efflux pump inhibitory activity against Mycobacterium smegmatis. Identification of TSA-5 by focusing on the modular MbtB_Cy domain paves the way for accelerating novel anti-TB antibiotic discoveries.
