... scalloptropomyosin, and various concentrations of TnI-fragment and TnC. The assays were performed at 15 °C in a mediumcontaining 50 mm KCl, 2 mm MgCl2,20mm Tris maleate(pH 6.8), 1 mm ATP, and 0.2 mm ... which binds tropomyosin, and trop-onin-I (TnI), which binds actin and inhibits actin–myo-sin interaction [2–4]. In relaxed muscle, TnI binds toactin and inhibits contraction. Upon muscle stimula-tion, ... redissolved in equivalent volumes of 5 M urea solution and then run on SDS ⁄ PAGE. Lanes a and d, inthe absence of both TnC and Ca2+; lanes b and e, in the presence of TnC and the absence of Ca2+;...