Interaction of HydSL hydrogenase from the purple sulfur bacterium Thiocapsa roseopersicina BBS with methyl viologen and positively charged polypeptides

The effect of polypeptides having different charge on the activity of Thiocapsa roseopersicina HydSL hydrogenase was studied. Strong inhibition was shown for poly-L-lysine bearing positive charge. The inhibition was reversible and competitive to methyl viologen, an electron acceptor, in the reaction of hydrogen oxidation catalyzed by the hydrogenase. Peptides carrying less positive charge had weaker inhibiting effect, while neutral and negatively charged peptides did not inhibit the hydrogenase. Molecular docking of poly-L-lysine to T. roseopersicina hydrogenase showed strong affinity of this polypeptide to the acceptor-binding site of the enzyme. The calculated binding constant is close to the experimentally measured value (Ki = 2.1 μM).