Artículos de revistas
The Sulfur Shift: An Activation Mechanism for Periplasmic Nitrate Reductase and Formate Dehydrogenase
Fecha
2013-09Registro en:
Cerqueira, Nuno M. F. S. A.; Fernandes, Pedro A.; González, Pablo Javier; Moura, José J. G.; Ramos, Maria J.; The Sulfur Shift: An Activation Mechanism for Periplasmic Nitrate Reductase and Formate Dehydrogenase; American Chemical Society; Inorganic Chemistry; 52; 19; 9-2013; 10766-10772
0020-1669
Autor
Cerqueira, Nuno M. F. S. A.
Fernandes, Pedro A.
González, Pablo Javier
Moura, José J. G.
Ramos, Maria J.
Resumen
A structural rearrangement known as sulfur shift occurs in some Mo-containing enzymes of the DMSO reductase family. This mechanism is characterized by the displacement of a coordinating cysteine thiol (or SeCys in Fdh) from the first to the second shell of the Mo-coordination sphere metal. The hexa-coordinated Mo ion found in the as-isolated state cannot bind directly any exogenous ligand (substrate or inhibitors), while the penta-coordinated ion, attained upon sulfur shift, has a free binding site for direct coordination of the substrate. This rearrangement provides an efficient mechanism to keep a constant coordination number throughout an entire catalytic pathway. This mechanism is very similar to the carboxylate shift observed in Zn-dependent enzymes, and it has been recently detected by experimental means. In the present paper, we calculated the geometries and energies involved in the sulfur-shift mechanism using QM-methods (M06/(6-311++G(3df,2pd),SDD)//B3LYP/(6-31G(d),SDD)). The results indicated that the sulfur-shift mechanism provides an efficient way to enable the metal ion for substrate coordination.