Unusual enzyme complexes in anaerobic aromatic metabolism of Geobacter metallireducens

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The anaerobic aromatic metabolism has extensively been studied in facultatively anaerobic bacteria. Due to limitations in the overall energy metabolism many key enzymatic processes differ in obligately anaerobic bacteria. E.g., the ATP-dependent, dearomatizing class I benzoyl-CoA reductase (BcrABCD-subunits, FeS-cofactors) is replaced by an ATP-independent class II BCR in obligate anaerobes (BamBCDEFGHI-subunits, W/FeS/SeCys/FAD-cofactors). In the last funding period we have isolated and characterized the previsouly unknown W/FeS-cluster containing active site subunits BamBC from Geobacter metallireducens, and the crystal structure of BamBC enabled first insights into the mechanism. Another unusual enzyme complex in G. metallireducens is p-cresol methylhydroxylase (PCMH, PcmGIJ-subunits) catalyzing the first steps in anaerobic p-cresol metabolism. It differs from other PCMHs by its tight location in the membrane, possibly in association with a cytochrome bc1-like complex (PcmCDEF-subunits) and by its unusual subunit/cofactor-composition. In the last funding period we have isolated and characterized the soluble PmcGIJ components. In the next funding period both entire enzyme complexes of the class II BCR and PCMH including the so far missing components will be isolated and studied by kinetic, spectroscopic and structural methodologies. A main objective is to obtain insights into the function of novel multi component enzyme complexes involved in unusual energy transduction/conservation processes in obligately anaerobic bacteria.