Effects of exogenous substrates on in vitro hydrogenase activation.

Reaction mixtures contained a desalted ΔiscR lysate (4 mg total protein·mL–1), 5 µM HydE, 5 µM HydF, 50 µM HydG, 2 µM CpI apoprotein, and the standard set of extrinsic substrates except those indicated (Δ). Substrate concentrations are provided in the Experimental Methods. Relevant analogs were added for selected conditions and are indicated in bold font type under Small Molecules Added. Abbreviations: Fe, Fe2+; S, S2–; Cys, cysteine; Tyr, tyrosine; DOPA, 3,4-dihydroxyphenylalanine.†CpI specific activities were measured after 24 hr of incubation and are shown in units of µmol H2 consumed·min–1 mg CpI–1 (n = 3–6).