3.D.1.4.2
[Ni²⁺-4Fe-4S] H⁺ translocating, quinone-independent ferredoxin:H⁺ oxidoreductase, EchA-F (Hedderich and Forzi, 2005; Künkel et al., 1998; Welte and Deppenmeier 2013) The Ech hydrogenases of M. mazei and M. barkeri have been characterized and were shown to pump protons (Welte et al., 2010).  The EchC and EcnF subunits include [Fe₄S₄] centers, and that in the EchC subunit exhibits a pH dependency to suggest that it plays a role in proton pumping (Forzi et al. 2005).  EchE has the NiFe center that converts 2H⁺ to H₂.  The transmembrane subuits are EchA and EchB (Welte and Deppenmeier 2013) The Ech hydrogenases of M. mazei and M. barkeri have been characterized and were shown to pump protons (Welte et al., 2010).  The EchC and EcnF subunits include [Fe₄S₄] centers, and that in the EchC subunit exhibits a pH dependency to suggest that it plays a role in proton pumping (Forzi et al. 2005).  EchE has the NiFe center that converts 2H⁺ to H₂.  The transmembrane subuits are EchA and EchB (Welte and Deppenmeier 2013).