Inhibition of skeletal muscle S1-myosin ATPase by peroxynitrite.
Exposure of myosin subfragment 1 (S1) to 3-morpholinosydnonimine (SIN-1) produced a time-dependent inhibition of the F-actin-stimulated S1 Mg(2+)-ATPase activity, reaching 50% inhibition with 46.7 +/- 8.3 microM SIN-1 for 8.7 microM S1, that is, at a SIN-1/S1 molar ratio of approximately 5.5. The inhibition was due to the peroxynitrite produced by SIN-1 decomposition because (1) decomposed SIN-1 was found to have no effect on S1 ATPase activity, (2) addition of SIN-1 in the presence of superoxide dismutase and catalase fully prevented inhibition by SIN-1, and (3) micromolar pulses of chemically synthesized peroxynitrite produced inhibition of F-actin-stimulated S1 Mg(2+)-ATPase activity. In parallel, SIN-1 produced the inhibition of the nonphysiological Ca(2+)-dependent and K(+)/EDTA-dependent S1 ATPase activity of S1 and, therefore, suggested that the inhibition of F-actin-stimulated S1 Mg(2+)-ATPase activity is produced by the oxidation of highly reactive cysteines of S1 (Cys(707) and Cys(697)), located close to the catalytic center. This point was further confirmed by the titration of S1 cysteines with 5,5'-dithiobis(2-nitrobenzoic acid) and by the parallel decrease of Cys(707) labeling by 5-(iodoacetamido)fluorescein, and it was reinforced by the fact that other common protein modifications produced by peroxynitrite, for example, protein carbonyl and nitrotyrosine formation, were barely detected at the concentrations of SIN-1 that produced more than 50% inhibition of the F-actin-stimulated S1 Mg(2+)-ATPase activity. Differential scanning calorimetry of S1 (untreated and treated with different SIN-1 concentrations) pointed out that SIN-1, at concentrations that generate micromolar peroxynitrite fluxes, impaired the ability of ADP.V(1) to induce the intermediate catalytic transition state and also produced the partial unfolding of S1 that leads to an enhanced susceptibility of S1 to trypsin digestion, which can be fully protected by 2 mM GSH.
Centre for Marine Sciences, Departamento de Química e Bioquímica, FCT, Universidade do Algarve 8005-139, Faro, Portugal.
Teresa
T
Tiago
Sónia
S
Simão
Manuel
M
Aureliano
Francisco Javier
FJ
Martín-Romero
Carlos
C
Gutiérrez-Merino
D000199:Actins / Q000378:metabolism; D000244:Adenosine Diphosphate / Q000378:metabolism; D000251:Adenosine Triphosphatases / Q000378:metabolism*; D000818:Animals; D002384:Catalysis; D003545:Cysteine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004795:Enzyme Stability; D008274:Magnesium / Q000378:metabolism / Q000494:pharmacology; D008981:Molsidomine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D015879:Myosin Subfragments / Q000037:antagonists & inhibitors* / Q000378:metabolism*; D010084:Oxidation-Reduction; D030421:Peroxynitrous Acid / Q000378:metabolism / Q000494:pharmacology*; D017510:Protein Folding; D011817:Rabbits; D024744:Skeletal Muscle Myosins / Q000037:antagonists & inhibitors; D013696:Temperature; D013997:Time Factors; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism
D000199:Actins; D015879:Myosin Subfragments; D030421:Peroxynitrous Acid; C002744:3-nitrotyrosine; D014443:Tyrosine; C002385:linsidomine; D000244:Adenosine Diphosphate; D008981:Molsidomine; D000251:Adenosine Triphosphatases; D024744:Skeletal Muscle Myosins; D008274:Magnesium; D003545:Cysteine