The Na+-translocating NADH:quinone oxidoreductase (NDH I) from Klebsiella pneumoniae and Escherichia coli: implications for the mechanism of redox-driven cation translocation by complex I.
Eukaryotic complex I integrated into the respiratory chain transports at least 4 H+ per NADH oxidized. Recent results indicate that the cation selectivity is altered to Na+ in complex I (NDH I) isolated from the enterobacteria Escherichia coli and Klebsiella pneumoniae. A sequence analysis illustrates the characteristic differences of the enterobacterial, Na+-translocating NDH I compared to the H+-translocating complex I from mitochondria. Special attention is given to the membranous NuoL (ND5, Nqo12) subunits that possess striking sequence similarities to secondary Na+/H+ antiporters and are proposed to participate in Na+ transport. A model of redox-linked Na+ (or H+) transport by complex I is discussed based on the ion-pair formation of a negatively charged ubisemiquinone anion with a positively charged Na+ (or H+).
Steuber
J
J
Mikrobiologisches Institut der Eidgenössischen Technishen Hochschule, Zurich, Switzerland. steuber@micro.biol.ethz.ch
D000595:Amino Acid Sequence; D004579:Electron Transport; D042967:Electron Transport Complex I; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics; D005798:Genes, Bacterial; D017136:Ion Transport; D007711:Klebsiella pneumoniae / Q000201:enzymology* / Q000235:genetics; D008954:Models, Biological; D008969:Molecular Sequence Data; D009247:NADH, NADPH Oxidoreductases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009876:Operon; D010084:Oxidation-Reduction; D021122:Protein Subunits; D017386:Sequence Homology, Amino Acid; D012964:Sodium / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism
D021122:Protein Subunits; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D009247:NADH, NADPH Oxidoreductases; D042967:Electron Transport Complex I