Funktion des CzcCB2A-Transporters

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The results obtained during the recent four years show that the CzcCBA transenvelope efflux complex, which catalyzes heavy metal resistance in Ralstonia metallidurans, is working in close interplay with other metal efflux systems. The cationic substrates of CzcCBA Co(II), Zn(II) and Cd(II) may be accepted from the cytoplasm or the periplasm or both compartments. The structure of the central subunit CzcA (RND protein family) of the complex will be solved, additionally, the structure of the related copper transporter CusA. The periplasmic substrate binding sites of either protein will be identified by site-directed mutagenesis. At least for CzcA, the importance of the cytoplasmic metal binding site for the cooperative transport behavior of this protein will be elucidated. Similar experiments will also be performed with the two P-type ATPases from R. metallidurans, ZntA and CadA. Involvement of the other RNDproteins from R. metallidurans for metal resistance in this bacterium will be analyzed. The uptake systems for cobalt, zinc and cadmium of R. metallidurans will be identified by expression in specific E. coli mutant strains. Finally, export of periplasmic cations as a mechanism of detoxification is only reasonable if re-uptake across the outer membrane is somehow limited. Therefore, the role of outer membrane proteins in metal resistance of R. metallidurans will also be evaluated.