Mechanismus und Kontrolle der Zink-Aufnahme im Modellorganismus Cupriavidus metallidurans CH34

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Sophisticated cellular biochemistry needs metals as cofactors. About 40% of all enzymes have metal cofactors. It is an interesting question how the correct metal is allocated to the right protein, which is especially complicated for divalent metal cations that have a similar ionic diameter and volume-tocharge ratios, and compete with each other for the metal binding sites in enzymes. The β−proteobacterium Cupriavidus metallidurans strain CH34 is able to keep its metal homeostasis under a variety of adverse conditions and became a prokaryotic model organism to study such a process. Most of its’ efflux systems, required to remove surplus metals from the cells, are known. In the first part of the proposal, many uptake systems for zinc were identified. We would like to continue by pursuing the following goals: (i) the inventory of zinc importers in strain CH34 shall be completed, (ii) the metal transport capacities of the importers from the metal-resistant strain CH34 shall be compared to those from E. coli, and (iii) the regulators of gene expression of the transport systems are to be identified. Goal number four stems from the unexpected observation that zinc starvation leads to disappearance of CzcA, the major component of the efflux protein complex CzcCBA. We would like to identify the mechanism behind this process.