Maria L. Ghirardi, Jordi Cohen, Paul King, Klaus Schulten, Kwiseon Kim, and
Michael Seibert.
[FeFe]-hydrogenases and photobiological hydrogen production.
In Lionel Vayssieres, editor, Solar hydrogen and
Nanotechnology, volume 6340 of Proceedings of the Society of
Photo-Optical Instrumentation Engineers, pp. 253-258, 2006.
GHIR2006
The promise of efficient, economic and renewable H2 photoproduction from water can potentially be met by green algae. These organisms are able to functionally link photosynthetic water oxidation to the catalytic recombination of protons and electrons to generate H2 gas through the activity of the hydrogenase enzyme. Green algal hydrogenases contain a unique metallo-catalytic H-cluster that performs the reversible H2 oxidation / evolution reactions. The H-cluster, located in the interior of the protein structure is irreversibly inactivated by O2, the by-product of water oxidation. We developed an Escherichi coli expression system to produce [FeFe]-hydrogenases from different biological sources and demonstrated that clostridial [FeFe]-hydrogenases have higher tolerance to O2 inactivation compared to their algal counterparts. We have been using computational simulations of gas diffusion within the Clostridium pasteurianum CpI hydrogenase to identify the pathways through which O2 can reach its catalytic site. Subsequently, we modify the protein structure at specific sites along the O2 pathways (identified by the computational simulations) by site-directed mutagenesis with the goal of generating recombinant enzymes with higher O2 tolerance. In this paper, we review the computational simulation work and report on preliminary results obtained through this strategy.
