Assembly of the membrane-bound FeS centre of the Na+-translocating NQR

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Iron is an essential element of life and participates in many cellular reactions. In complex with sulfur, two or more Fe atoms can form iron-sulfur clusters which facilitate many different enzymatic reactions. In the respiratory chain, many enzymes rely on FeS centers to catalyse redox-driven proton or Na+ transport. Typically, the FeS centers are bound to the peripheral part of the respiratory enzyme, but the Na+ -translocating NADH:quinone oxidoreductase (NQR) harbors an unprecedented FeS cluster bound within the membrane part of the complex. The NQR is a respiratory Na+ pump found in many gram-negative bacteria, including pathogenic Vibrio cholerae. In this collaborative research project, the properties and the assembly of this novel, membrane-bound FeS cluster of NQR will be studied using microbiological, biochemical and biophysical techniques. Previous results suggested an unusual ligation of the cluster which will be studied by X-ray crystallographic structure determination of improved crystals of holo-NQR. In addition, we will address the pathway of insertion of the FeS cluster to NQR by studying the structure and function of the FeS carrier protein NqrM. Our goals are the complete reconstruction of the iron-sulfur delivery pathway to the novel FeS center in NQR, and an understanding of the catalytic role of this membrane-bound FeS center in redox-driven Na+ -transport by NQR.