Structure and Function of Metallo Proteins of the Anaerobic CO Metabolism

Carbon monoxide can be used by various aerobic bacteria and anaerobic bacteria and archaea as sole source of carbon and energy. In anaerobic bacteria and archaea a set of three metalloproteins, the corrinoid iron-sulfur protein, the Ni,Fe-containing acetyl-CoA synthase and the Ni,Fe-containing carbon monoxide dehydrogenase (CODHase), are essential for both processes. The assembly of the complex active site clusters of the Ni,Fe-containing enzymes is dependent on ATPases, which are supposed to assist the insertion of Ni into the folded enzymes.
The research proposal focuses on the function and assembly of the active site cluster of Ni,Fe-containing CODHases. The crystal structure of a CODH from Carboxydothermus hydrogenoformans has been solved at true atomic resolution (dmin < 1.2 ?) and a heterologous expression system in Escherichia coli yielding homogenous and highly active CODH preparations under anoxic conditions has been established. The recombinant production allows to probe the catalytic oxidation of carbon monoxide at the [Ni-4Fe-4/5S] cluster by site directed mutagenesis in combination with high resolution x-ray crystallography. The role of the ATPases in metal insertion into CODHases will be investigated by biochemical and crystallographic approaches. Heterologous expression systems for three ATPases have been established and diffracting crystals for one enzyme are available.