title: Ramoplanin inhibits bacterial transglycosylases by binding as a dimer to lipid II.
abstract: Ramoplanin is a lipglycodepsipeptide antibiotic that inhibits peptidoglycan biosynthesis. Its mechanism of action has been the subject of debate. It was originally proposed to inhibit the MurG step of peptidoglycan synthesis by binding Lipid I. In this paper, we report that ramoplanin inhibits bacterial transglycosylases by binding to Lipid II, the substrate for these enzymes. The inhibition curves reveal that the inhibitory species has a stoichiometry of 2:1 ramoplanin:Lipid II. A Job titration confirms that ramoplanin binds as a dimer to Lipid II. The apparent dissociation constant is in the nanomolar range, which is unusually low given the nature of the interacting species. We show that Lipid II binding is coupled to the formation of a higher order species, which may explain the tight binding. We also present a testable model for the binding-competent dimeric conformation of ramoplanin.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
authors.forename: Yanan
authors.initials: Y
authors.lastname: Hu
authors.forename: Jeremiah S
authors.initials: JS
authors.lastname: Helm
authors.forename: Lan
authors.initials: L
authors.lastname: Chen
authors.forename: Xiang-Yang
authors.initials: XY
authors.lastname: Ye
authors.forename: Suzanne
authors.initials: S
authors.lastname: Walker
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D047630:Depsipeptides; D019281:Dimerization; D004305:Dose-Response Relationship, Drug; D006602:Hexosyltransferases / Q000037:antagonists & inhibitors*; D007700:Kinetics; D009097:Multienzyme Complexes / Q000037:antagonists & inhibitors*; D002267:Muramoylpentapeptide Carboxypeptidase; D017351:N-Acetylglucosaminyltransferases / Q000378:metabolism; D046915:Penicillin-Binding Proteins; D010456:Peptides, Cyclic / Q000378:metabolism / Q000494:pharmacology*; D010458:Peptidyl Transferases / Q000037:antagonists & inhibitors*; D011487:Protein Conformation; D014538:Uridine Diphosphate N-Acetylmuramic Acid / Q000031:analogs & derivatives* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D001426:Bacterial Proteins; D002352:Carrier Proteins; D047630:Depsipeptides; D009097:Multienzyme Complexes; D046915:Penicillin-Binding Proteins; D010456:Peptides, Cyclic; D014538:Uridine Diphosphate N-Acetylmuramic Acid; C069249:muramyl-NAc-(pentapeptide)pyrophosphoryl-undecaprenol; C041438:ramoplanin; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D017351:N-Acetylglucosaminyltransferases; C064057:UDP-N-acetylglucosamine-N-acetylmuramyl-(pentapeptide)pyrophosphoryl-undecaprenol N-acetylglucosamine transferase; D002267:Muramoylpentapeptide Carboxypeptidase