Modeling three-dimensional structure of two closely related Ni-Fe hydrogenases.

The results of homology modeling of HydSL, a NiFe-hydrogenase from purple sulfur bacterium Thiocapsa roseopersicina BBS, and deep-water bacterium Alteromonas macleodii deep ecotype are presented in this work. It is shown that the models have larger confidence level than earlier published ones; full-size models of these enzymes are presented for the first time. The C-end fragment of small subunit of T. roseopersicina hydrogenase is shown to have random orientation in relation to the main protein globule. The obtained models of this enzyme have a large number of ion pairs, as well as thermostable HydSL hydrogenase from Allochromatium vinosum, in contrast to thermostable HydSL hydrogenase from Alt. macleodii and thermolabile HydAB hydrogenase from Desulfovibrio vulgaris. The possible determinant of oxygen stability of studied hydrogenases could be the lack of several intramolecular tunnels. Hydrophobic and electrostatic surfaces were mapped in order to find out possible pathways of coupling hydrogenase to electron-transferring chains, as well as methods for construction of artificial photobiohydrogen-producing systems.