title: A Second, Druggable Binding Site in UDP-Galactopyranose Mutase from Mycobacterium tuberculosis?
abstract: UDP-galactopyranose mutase (UGM), a key enzyme in the biosynthesis of mycobacterial cell walls, is a potential target for the treatment of tuberculosis. In this work, we investigate binding models of a non-substrate-like inhibitor, MS-208, with M. tuberculosis UGM. Initial saturation transfer difference (STD) NMR experiments indicated a lack of direct competition between MS-208 and the enzyme substrate, and subsequent kinetic assays showed mixed inhibition. We thus hypothesized that MS-208 binds at an allosteric binding site (A-site) instead of the enzyme active site (S-site). A candidate A-site was identified in a subsequent computational study, and the overall hypothesis was supported by ensuing mutagenesis studies of the A-site. Further molecular dynamics studies led us to propose that MS-208 inhibition occurs by preventing complete closure of an active site mobile loop that is necessary for productive substrate binding. The results suggest the presence of an A-site with potential druggability, opening up new opportunities for the development of novel drug candidates against tuberculosis.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
authors.forename: Yun
authors.identifier: 0000-0003-3365-4679
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
authors.forename: Cinzia
authors.initials: C
authors.lastname: Colombo
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.
authors.forename: Jijin R A
authors.initials: JR
authors.lastname: Kuttiyatveetil
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.
authors.forename: Nataliya
authors.initials: N
authors.lastname: Zalatar
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.
authors.forename: Karin E
authors.initials: KE
authors.lastname: van Straaten
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
authors.forename: Sankar
authors.initials: S
authors.lastname: Mohan
authors.affiliation: Department of Chemistry, University of Saskatchewan, 110 Science Place, Saskatoon, Saskatchewan, S7N 5C9, Canada.
authors.forename: David A R
authors.initials: DA
authors.lastname: Sanders
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC, V5A 1S6, Canada.
authors.forename: B Mario
authors.initials: BM
authors.lastname: Pinto
mesh_terms: D001665:Binding Sites / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology*; D019751:Intramolecular Transferases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009169:Mycobacterium tuberculosis / Q000201:enzymology*; D011720:Pyrazoles / Q000737:chemistry / Q000494:pharmacology*; D013329:Structure-Activity Relationship
chemical_list: D004791:Enzyme Inhibitors; C000622106:MS-208; D011720:Pyrazoles; D019751:Intramolecular Transferases; C098051:UDP-galactopyranose mutase
keywords: STD NMR; UDP-galactopyranose mutase; enzyme kinetics; inhibitors; molecular modeling