Insights into the mechanism of electron transfer and sodium translocation of the Na+-pumping NADH:quinone oxidoreductase

► Na+-NQR is a respiratory enzyme essential in the metabolism of many marine and pathogenic bacteria. ► Na+-NQR selectively translocates only Na+ across the cell membrane. ► Na+-NQR has five redox cofactors: FAD, 2Fe-2S center, two covalently bound FMN's and riboflavin. ► Coupling of Na+ transport to redox reactions is indirect. ► Coupling is likely mediated by conformational changes.