Exploring the gas access routes in a [NiFeSe] hydrogenase using crystals pressurized with krypton and oxygen

摘要

Hydrogenases are metalloenzymes that catalyse both H(2)evolution and uptake. They are gas-processing enzymes with deeply buried active sites, so the gases diffuse through channels that connect the active site to the protein surface. The [NiFeSe] hydrogenases are a special class of hydrogenases containing a selenocysteine as a nickel ligand; they are more catalytically active and less O-2-sensitive than standard [NiFe] hydrogenases. Characterisation of the channel system of hydrogenases is important to understand how the inhibitor oxygen reaches the active site to cause oxidative damage. To this end, crystals ofDesulfovibrio vulgarisHildenborough [NiFeSe] hydrogenase were pressurized with krypton and oxygen, and a method for tracking labile O(2)molecules was developed, for mapping a hydrophobic channel system similar to that of the [NiFe] enzymes as the major route for gas diffusion.