S-NO-actin: S-nitrosylation kinetics and the effect on isolated vascular smooth muscle

We describe the modification of reactive actin sulfhydryls by S-nitrosoglut athione. Kinetics of S-nitrosylation and denitrosylation suggest that only one cysteine of actin is involved in the reactions. By using the bifunction al sulfhydryl cross-linking reagent N,N'-1,4-phenylenebismaleimide and the monofunctional reagent N-iodoacetyl-N'-(5-sulpho-1-naphthyl)ethylenediamine , we identified this residue as Cys(374). The time course of filament forma tion followed by high-shear viscosity changes revealed that S-nitrosylated G-actin polymerizes less efficiently than native monomers. The observed dec rease in specific viscosity at steady state is due mainly to a marked inhib ition of filament end-to-end annealing and, partially, to a reduction in F- actin concentration. Finally, S-nitrosylated actin acts as nitric oxide don or showing a fast, potent vasodilating activity at unusually low concentrat ions, being comparable with that of low molecular weight nitrosothiols.