FIG. 7.

Interactions between the auxiliary proteins in the maturation of hydrogenases 1 (HYD1; HyaB), 2 (HYD2; HybC), and 3 (HYD3; HycE). The model highlights the role of HybG and HybF in guiding the maturation machinery to hydrogenase 1 and 2 maturation under anaerobic respiration. Under fermentative conditions HypC and HypA direct the components to the maturation of hydrogenase 3. The left part represents postulated Fe incorporation by a complex between HypD and HypC/HybG which is followed by the Ni incorporation by HypB and HypA/HybF, shown on the right side. The weak effects of HypA on hydrogenase 1 and 2 maturation and of HybF on hydrogenase 3 maturation as well as the interaction of HypC with hydrogenases 1 and 2 when the homolog is missing are not depicted, for the sake of clarity.