Modification of Actomyosin Atpaseby Anti-Troponins C and I

1)Antibodies against rabbit skeletal muscle troponin C and I were raised in goats. The effect of the antibodies was examined on the calcium-sensitive ATPase of natural actomyosin (myosin B) and actomyosin containing tropomyosin and various combinations of three troponin components (C-I-T). 2) Both anti-troponin C and anti-troponin I accelerated the ATPase of natural actomyosin and actomyosin in the presence of tropomyosin and three troponin components about 2-fold at high calcium concentration (4.6x10-5 M). At low calcium concentration (2.4x10-8 M), both antibodies also potentiated the ATPase 2-to 3-fold. 3) In the presence of incomplete combinations of troponin components (troponin I, troponin I-T or troponin C-I), anti-troponin I did not affect the ATPase of actomyosin at all calcium concentrations. 4) In the presence of troponin C-I, anti-troponin C accelerated the actomyosin ATPase definitely at high calcium concentration, but inhibited it at low calcium concentration to some extent. 5) Both anti-troponin I and anti-troponin C coprecipitated with natural actomyosin (actomyosintropomyosin-troponin C-I-T) regardless of calcium concentrations. On the other hand, actomyosin containing tropomyosin-troponin I-C was found to coprecipitate with anti-troponin C, but not with anti-toponin I. 6) When troponin T was replaced by its chymotryptic subfragment, i.e. troponin T2, the actomyosin ATPase was not affected by anti-troponin I, but was potentiated by anti-troponin C at all calcium concentrations.