Amino acid variants of the HybB membrane subunit of Escherichia coli [NiFe]-hydrogenase-2 support a role in proton transfer.

[NiFe]-hydrogenase (Hyd) 2 of Escherichia coli has been proposed to generate proton motive force during H -oxidation, which it is dependent on if cells are incubated anaerobically with glycerol to drive reverse H -production. The integral membrane subunit HybB is required for proton transfer (PT) by Hyd-2 but has no cofactor. To provide evidence for PT by HybB, we analyzed the roles of conserved amino acid residues in a predicted proton channel.