P-82 - Peroxynitrite versus decavanadate protein oxidative modifications: the case of myosin

Abstract

In many diseases as well as during biological aging peroxynitrite (ONOO-) reacts with sarcomeric proteins, such as myosin and actin, in skeletal muscle (Steinberg, Circ. Res. 2013). We have previously demonstrated that exposure of purified myosin subfragment-1 (S1) to submicromolar fluxes of peroxynitrite produces strong inhibition of the actomyosin-ATPase activity with an IC50 of inhibition of 47 µM, being the inhibition due to the oxidation of the highly-reactive Cys on myosin (Tiago et al., Biochemistry 2006; Free Radic Res. 2010). In the present communication we further explore these studies by analyzing the exposition of myosin to peroxynitrite using ADP.V analogues, as well as the exposition to decavanadate (V10), a toxic ion previously described to bind at the myosin back door. Conversely to peroxynitrite, it was observed that decavanadate exposition induces the oxidation of a core Cys on myosin and not the highly-reactive Cys, whereas a strong inhibition of the actomyosin-ATPase activity was determined (IC50=2.7 µM). It was also observed that myosin suffers modifications at Lys-84 upon peroxynitrite exposition. In sum, myosin is more sensitive to oxidative modifications mediated by decavanadate than by peroxynitrite.