Formate hydrogenlyase is needed for proton-potassium exchange through the F0F1-ATPase and the TrkA system in anaerobically grown and glycolysing Escherichia coli.

Anaerobically grown and glycolysing Escherichia coli produced H2 and carried out H+-K+-exchange in two steps, the first of which had the fixed stoichiometry for DCCD-sensitive fluxes (2H+/K+), and the second one had a variable stoichiometry for DCCD-sensitive fluxes. H2 production and the 2H+/K+-exchange were lost in the DeltafdhF or DeltahycA-H mutant. In the DeltafdhF mutant, H+-K+-exchange with Km for K+-uptake of 2.3 mM and less K+-gradient between the cytoplasm and the medium were observed. H2 production and H+-K+-exchange with a high Km for K+-uptake were carried out in the uncD mutant; however, both H2 production and H+-K+-exchange were lost in the Deltaunc or uncE mutant. H2 production was observed in the trkA trkD kdpA mutant. It was displayed in protoplasts with increased membrane permeability when donor or acceptor of reducing equivalents-formate with DTT or NADH respectively-was added. The F0F1 and the TrkA(H) or the F0 and the TrkA(G) had been assumed to form the united supercomplexes, functioning as a H+-K+-pump or antiporter respectively (for review see Bioelectrochem Bioenerg 33:1, 1994). Results allow the proposal that H2 production by FHL has a relationship with the H+-K+-exchange through a H+-K+-pump and via an H+-K+-antiporter. Formate and NADH can serve as a donor and an acceptor of reducing equivalent respectively, for operation of such supercomplexes.

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