, Volume 21, Issue 2, pp 171-181

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

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We describe the modification of reactive actin sulfhydryls by S-nitrosoglutathione. Kinetics of S-nitrosylation and denitrosylation suggest that only one cysteine of actin is involved in the reactions. By using the bifunctional 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 Cys374. The time course of filament formation followed by high-shear viscosity changes revealed that S-nitrosylated G-actin polymerizes less efficiently than native monomers. The observed decrease in specific viscosity at steady state is due mainly to a marked inhibition of filament end-to-end annealing and, partially, to a reduction in F-actin concentration. Finally, S-nitrosylated actin acts as nitric oxide donor showing a fast, potent vasodilating activity at unusually low concentrations, being comparable with that of low molecular weight nitrosothiols.