title: A cytochrome that can pump sodium ion.
abstract: Previous studies have shown that the bacterium, Vitreoscilla, generates a respiratory-driven delta psi Na+. Two major respiratory electron transport proteins, NADH dehydrogenase (NADH:Quinone oxidoreductase), and cytochrome o terminal oxidase are candidates for the electrogenic Na+ pumping that mediates the delta psi Na+ formation. The NADH oxidase activity of the membranes was enhanced more by Na+ than by Li+. The NADH:Quinone oxidoreductase activity in the respiratory chain was enhanced by Na+ and Li+, whereas the quinol oxidase activity of cytochrome o was enhanced specifically by Na+, and not by Li+, K+, or choline. Purified cytochrome o, reconstituted into Na(+)-loaded liposomes in the right-side-out orientation, catalyzed a net Na+ extrusion when energized with Q1H2(1). In nonloaded inside-out proteoliposomes, this cytochrome catalyzed a net uptake of 22Na+ when energized with ascorbate/TMPD. Both Na(+)-pumping activities were inhibited by CN-. These results are consistent with the Vitreoscilla cytochrome o being a redox-driven Na+ pump.
authors: Department of Biology, Illinois Institute of Technology, Chicago 60616.
authors: B J
authors: BJ
authors: Efiok
authors: D A
authors: DA
authors: Webster
mesh_terms: D001420:Bacteria, Aerobic / Q000378:metabolism*; D001693:Biological Transport, Active / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D003573:Cytochrome b Group; D003580:Cytochromes / Q000302:isolation & purification / Q000378:metabolism*; D029968:Escherichia coli Proteins; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D009097:Multienzyme Complexes / Q000378:metabolism; D009245:NADH Dehydrogenase / Q000378:metabolism; D009247:NADH, NADPH Oxidoreductases / Q000378:metabolism; D010089:Oxidoreductases, N-Demethylating / Q000378:metabolism; D012964:Sodium / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D003573:Cytochrome b Group; D003580:Cytochromes; D029968:Escherichia coli Proteins; D009097:Multienzyme Complexes; C017168:cytochrome bo, E coli; D008094:Lithium; D012964:Sodium; D010089:Oxidoreductases, N-Demethylating; C022726:tetramethylphenylenediamine oxidase; C023107:NADH oxidase; D009247:NADH, NADPH Oxidoreductases; D009245:NADH Dehydrogenase