Interconnections of metallo enzyme synthesis machineries in Geobacter metallireducens: cofactor assembly and function of W-/FeS-containing BamB

• Applicant: Professor Dr. Matthias Boll
• Subject Area: Biochemistry
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 311008651

Aromatic compounds can be fully degraded by anaerobic bacteria using oxygenase-independent pathways. Here, most monocyclic aromatic growth substrates are converted to the central intermediate benzoyl-CoA, that is dearomatized by reductases to cyclic 1,5-dienoyl-CoA at an extremely low redox potential (E° = -622 mV). Obligate anaerobes such as the Fe(III) respiring model organism Geobacter metallireducens employ a W-cofactor containing class II benzoyl-CoA reductase. The active site component BamB belongs to the W-containing family of aldehyde:ferredoxin oxidoreductases. A Bam(BC)2 complex with four [4Fe-4S] clusters and a catalytic W-bispterin (bisWPT)-cofactor has initially been characterized. The W-atom is coordinated by five S-atoms from the pterin and the protein and by a yet non-identified 6th, probably cyano-ligand. The 6th ligand mediates electron transfer from the reduced W to the benzene ring representing an unprecedented mode of catalysis among Mo/W-cofactor containing enzymes. The project aims (i) to unravel the nature and function of the BamB active site by a number of spectroscopic and structural methodologies with a special focus on the crucial 6th W-ligand; (ii) to elucidate the synthesis and assembly of the unusual bisWPT-cofactor of BamB, in particular the function of the bamL-encoded chaperone; and (iii) to shed light into the interconnections of metallo enzyme synthesis in G. metallireducens that is capable of producing Mo-/W-/NiFe/FeS-enzymes in parallel. The whole project is based on intensive methodical and topic-related collaborations with numerous members of SPP1927 and international experts.

• DFG Programme: Priority Programmes
• Subproject of: SPP 1927: Iron-Sulfur for Life