FIG. 1.
Proposed conceptual model for the electron transfer pathway of H2 oxidation by Desulfovibrio. Three classes of periplasmic hydrogenases (NiFe, NiFeSe, and Fe-only hydrogenases [Hase]) may be involved in H2 metabolism. The electrons (e−) generated from H2 oxidation in the periplasm are transferred to the cytochrome c3 (Cyc) network for delivery to transmembrane electron carriers (TMC) and then possibly into the menaquinone (MK) pool, creating reduced menaquinone (MKH2) within the inner membrane (IM) or directly across the inner membrane for sulfate reduction in the cytoplasm. The Mop complex described here may be one of these TMC. The protons generated from H2 oxidation in the periplasm drive ATP synthesis (by the ATP synthase), as they contribute directly to a proton gradient. The protons imported through ATP synthase are also used in the sulfate reduction pathway. H2 is either supplied externally or produced in the cytoplasm through organic substrate degradation.