Molecular and functional properties of the Na+ -translocating NADH:quinone oxidoreductase (Na+ -NQR) from Vibrio cholerae

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The bacterium Vibrio cholerae, the causative agent of Cholera disease, utilizes the Na+-translocating NADH:quinone oxidoreductase (Na+-NQR) to generate a Na+ motive force. The Na+-NQR is a membrane-bound enzyme complex consisting of the six subunits NqrABCDEF. This redox-driven pump with a molecular mass of 220 kDa catalyzes the first step in the respiratory chain of V. cholerae and couples the exergonic oxidation of NADH to the endergonic translocation of Na+ from the cytoplasm to the periplasm. The mechanism of redox-driven Na+ transport by the Na+-NQR is unknown. Our long-term goal is to understand this process at atomic scale. To this end, we will analyze the electron transfer and Na+ translocation events using the solubilized and reconstituted pump, and characterize and crystallize subcomplexes for the determination of the 3D structure.