The C-terminally truncated NuoL subunit (ND5 homologue) of the Na+-dependent complex I from Escherichia coli transports Na+.
The NADH:quinone oxidoreductase (complex I) from Escherichia coli acts as a primary Na+ pump. Expression of a C-terminally truncated version of the hydrophobic NuoL subunit (ND5 homologue) from E. coli complex I resulted in Na+-dependent growth inhibition of the E. coli host cells. Membrane vesicles containing the truncated NuoL subunit (NuoLN) exhibited 2-4-fold higher Na+ uptake activity than control vesicles without NuoLN. Respiratory proton transport into inverted vesicles containing NuoLN decreased upon addition of Na+, but was not affected by K+, indicating a Na+-dependent increase of proton permeability of membranes in the presence of NuoLN. The His-tagged NuoLN protein was solubilized, enriched by affinity chromatography, and reconstituted into proteoliposomes. Reconstituted His6-NuoLN facilitated the uptake of Na+ into the proteoliposomes along a concentration gradient. This Na+ uptake was prevented by EIPA (5-(N-ethyl-N-isopropyl)-amiloride), which acts as inhibitor against Na+/H+ antiporters.
Mikrobiologisches Institut der Eidgenössischen Technischen Hochschule, ETH-Zentrum, Schmelzbergstrasse 7, CH-8092 Zürich, Switzerland. fritz-steuber@micro.biol.ethz.ch
Julia
J
Steuber
D001483:Base Sequence; D002463:Cell Membrane Permeability; D004269:DNA, Bacterial / Q000235:genetics; D042967:Electron Transport Complex I; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017136:Ion Transport; D007700:Kinetics; D008954:Models, Biological; D008958:Models, Molecular; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D017494:Proton Pumps / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion; D012964:Sodium / Q000378:metabolism*
D004269:DNA, Bacterial; D029968:Escherichia coli Proteins; D021122:Protein Subunits; D017494:Proton Pumps; D011994:Recombinant Proteins; D012964:Sodium; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I