Multidrug transport protein norM from vibrio cholerae simultaneously couples to sodium- and proton-motive force.
Membrane transporters belonging to the multidrug and toxic compound extrusion family mediate the efflux of unrelated pharmaceuticals from the interior of the cell in organisms ranging from bacteria to human. These proteins are thought to fall into two classes that couple substrate efflux to the influx of either Na(+) or H(+). We studied the energetics of drug extrusion by NorM from Vibrio cholerae in proteoliposomes in which purified NorM protein was functionally reconstituted in an inside-out orientation. We establish that NorM simultaneously couples to the sodium-motive force and proton-motive force, and biochemically identify protein regions and residues that play important roles in Na(+) or H(+) binding. As the positions of protons are not available in current medium and high-resolution crystal structures of multidrug and toxic compound extrusion transporters, our findings add a previously unrecognized parameter to mechanistic models based of these structures.
From the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom.
Yoonhee
Y
Jin
From the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom.
Asha
A
Nair
From the Department of Pharmacology, University of Cambridge, Cambridge CB2 1PD, United Kingdom hwv20@cam.ac.uk.
Hendrik W
HW
van Veen
D017920:Antiporters / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001224:Aspartic Acid / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D001692:Biological Transport; D015153:Blotting, Western; D002462:Cell Membrane / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004996:Ethidium / Q000378:metabolism; D018698:Glutamic Acid / Q000737:chemistry / Q000378:metabolism; D013294:Lactococcus lactis / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D011510:Proteolipids / Q000378:metabolism; D018892:Proton-Motive Force; D011522:Protons; D012964:Sodium / Q000378:metabolism*; D014734:Vibrio cholerae / Q000235:genetics / Q000378:metabolism*
D017920:Antiporters; D001426:Bacterial Proteins; C114619:NorM protein, bacteria; D011510:Proteolipids; D011522:Protons; C020485:proteoliposomes; D001224:Aspartic Acid; D018698:Glutamic Acid; D004247:DNA; D012964:Sodium; D004996:Ethidium
Bioenergetics; Enzyme Mechanisms; Membrane Proteins; Membrane Transport; Multidrug Transporters