title: Differentiating ligand and inhibitor interactions of a single antiporter.
abstract: Regulatory mechanisms of ion and solute transporters are in focus of biomedical and biochemical studies and build a key for disease therapies. Inhibition of sodium/proton exchangers efficiently prevents ischemic heart disease and reperfusion development in humans, but molecular mechanisms behind are not clear. Using single-molecule force spectroscopy we observe the binding of the inhibitor 2-aminoperimidine (AP) to sodium/proton antiporters NhaA from Escherichia coli. Deactivating interactions were significantly suppressed at enhanced sodium concentrations of 200 mM as well as in the pH-locked inactive conformation of NhaA. New molecular interactions were quantified and localized within the protein occurring upon a competitive inhibitor binding. The inhibitor, which was targeted and bound to the ligand-binding pocket, altered interactions established at alpha-helix IX. These molecular mechanisms deactivating the antiporter were different to those established upon ligand binding and activation of NhaA.
authors.affiliation: BIOTEC, University of Technology, 01307 Dresden, Germany.
authors.forename: Alexej
authors.initials: A
authors.lastname: Kedrov
authors.forename: Christine
authors.initials: C
authors.lastname: Ziegler
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Muller
mesh_terms: D001665:Binding Sites; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004926:Escherichia coli / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D018625:Microscopy, Atomic Force; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D011799:Quinazolines / Q000378:metabolism* / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors*
chemical_list: C114362:2-aminoperimidine; D029968:Escherichia coli Proteins; D008024:Ligands; D011799:Quinazolines; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium