S C el-Saleh

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Inhibition of muscle force development by acidic pH is a well known phenomenon, yet the exact mechanism by which a decrease in pH inhibits the Ca2+-activated force in striated myofilaments remains poorly understood. Whether or not the deactivation by acidic pH involves direct competition between Ca2+ and protons for regulatory binding sites on fast skeletal(More)
Several conflicting reports have been made regarding the affinity of myosin heads (subfragment 1 and heavy meromyosin (HMM) for regulated actin (actin complexed with tropomyosin and troponin) at low ionic strength (mu = 18-50 mM) and whether or not this interaction is Ca2+ sensitive (Chalovich, J. M., and Eisenberg, E. (1982) J. Biol. Chem. 257, 2432-2437;(More)
It has been possible to specifically label rabbit skeletal muscle actin at Lys-237 with 2,4-pentanedione, producing an enamine. This reaction can be reversed with hydroxylamine. The modification can be carried out with actin in either the G- or F-forms and does not affect polymerization-depolymerization. The modification does affect, however, the(More)
1. The intrinsic fluorescence of epoxysuccinyl-inhibited calpain II undergoes a Ca2(+)-dependent decrease which contrasts with the increase observed for calmodulin. 2. Calpain II was inhibited by the calmodulin antagonist toluidinylnaphthalenesulfonate (TNS), and a Ca2(+)-dependent increase in TNS fluorescence intensity was observed for(More)
In previous work, we (El-Saleh, S., Theiret, R., Johnson, P., and Potter, J. D. (1984) J. Biol. Chem. 259, 11014-11021) presented evidence that Ca2+ activation of skeletal myofilaments depends on a specific actin domain. We showed that rabbit skeletal thin filaments reconstituted with actin modified at Lys-237 activate heavy meromyosin X Mg2+-ATPase(More)
Although regulatory Ca2+-binding domains of calmodulin (CaM) and troponin C (TnC) are similar, it is interesting that agents that act as CaM antagonists appear to be TnC "agonists" in that they sensitize cardiac myofilaments to activation by Ca2+ (El-Saleh, S., and Solaro, R. J. (1987) Biophys. J. 51, 325 (abstr.). This indicates that the effects of agents(More)
Only the 80-kD catalytic subunit of smooth muscle calpain II shows a change in intrinsic fluorescence on binding calcium, but both the 80-kD and 30-kD subunits show fluorescence changes in bound toluidinyl-naphthalenesulphonate as a result of calcium binding. Both subunits also show changes in intrinsic fluorescence in the presence of calmidazolium and(More)
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