A Molybdopterin Oxidoreductase Is Involved in H 2 Oxidation in Desulfovibrio desulfuricans G20

Abstract

Three mutants deficient in hydrogen/formate uptake were obtained through screening of a transposon mutant library containing 5,760 mutants of Desulfovibrio desulfuricans G20. Mutations were in the genes encoding the type I tetraheme cytochrome c ₃ ( cycA ), Fe hydrogenase ( hydB ), and molybdopterin oxidoreductase ( mopB ). Mutations did not decrease the ability of cells to produce H ₂ or formate during growth. Complementation of the cycA and mopB mutants with a plasmid carrying the intact cycA and/or mopB gene and the putative promoter from the parental strain allowed the recovery of H ₂ uptake ability, showing that these specific genes are involved in H ₂ oxidation. The mop operon encodes a periplasm-facing transmembrane protein complex which may shuttle electrons from periplasmic cytochrome c ₃ to the menaquinone pool. Electrons can then be used for sulfate reduction in the cytoplasm.