Structure/Function Relationships of [NiFe]- and [FeFe]-Hydrogenases

Abstract

4286 6.1. Oxidized Inactive States of the Ni−Fe Site and Radiation Effects 4286 6.2. Oxidative Damage of FeS Clusters in [FeFe]-Hydrogenases 4288 6.3. Hydrophobic Tunnels in [NiFe]-Hydrogenases 4288 6.4. Hydrophobic Tunnels in [FeFe]-Hydrogenase 4291 6.5. Hydrogen Sensors Related to [NiFe]-Hydrogenases 4292 6.6. Oxygen-Insensitive [NiFe]-Hydrogenases from Ralstonia eutropha 4294 7. Evolutionary Relationships of Hydrogenases to Other Proteins 4294 7.1. Comparison of [NiFe]-Hydrogenase with Complex I 4294 7.2. Comparison of [FeFe]-Hydrogenase to Narf-like Proteins 4296 8. Substrate Binding and Catalysis 4297 8.1. [NiFe]-Hydrogenases 4297 8.2. [FeFe]-Hydrogenases 4297 8.3. Comparison of Active Redox States in [NiFe]and [FeFe]-Hydrogenases 4299 9. Concluding Remarks 4299 10. Acknowledgments 4300 11. Note Added after ASAP Publication 4300 12. References 4300

Probing the Origin of the Metabolic Precursor of the CO Ligand in the Catalytic Center of [NiFe] Hydrogenase

“…Although all three glycerolderived carbons occur as CO ligands, the terminal carbon atoms appear to be preferentially incorporated into the cofactor. This observation is supported by a control experiment using [2][3][4][5][6][7][8][9][10][11][12][13] C]glycerol as the substrate (supplemental Fig. S1).…”

“…2), supporting the notion that acetate is not the metabolic precursor of the carbonyl ligand of the R. eutropha [NiFe] hydrogenase. 2 , and O 2 -It has been shown previously that externally added CO is incorporated as carbonyl ligand into E. coli hydrogenase-2 and recombinant RH (12,14). This observation suggests that CO may be released from an internal metabolite prior to insertion into the [Ni-Fe] cofactor.…”

“…Hydrogenases are metalloenzymes catalyzing the reversible heterolytic cleavage of dihydrogen into two protons and two electrons (1,2). According to the metal content of the active site, these enzymes are classified into three groups of [NiFe] and [FeFe] hydrogenases and [Fe] hydrogenases, all of which emerged from convergent lines of evolution (3).…”

Enzymatic activity mastered by altering metal coordination spheres

“…This enzyme carries out the simplest oxidation-reduction reaction: proton reduction and hydrogen oxidation [23,24]. …”

“…The nickel-iron hydrogenases are ab heterodimers composed of a small (b-subunit) and a large subunit (a-subunit), whose structures have been determined from different organisms [23]. The small subunit contains three iron-sulfur clusters, and the larger subunit holds a binuclear Ni-Fe cluster; the catalytic site.…”