Evidence that the Sr2+ activation properties of cardiac troponin C are altered when substituted into skinned skeletal muscle fibers.
Troponin C (TnC) was extracted from skinned skeletal muscle fibers by a method similar to that used previously on myofibrils (Zot, H.G., and Potter, J.D. (1982) J. Biol. Chem. 257, 7678-7683) and replaced with either skeletal (fast-twitch) or cardiac TnC. The relationship between isometric tension and Sr2+ concentration remained essentially the same before removal and after replacement with skeletal or cardiac TnC. Therefore, the origin of the TnC made no difference in the Sr2+ activation properties of the skinned fiber. In contrast, the activation of skinned cardiac fibers is approximately an order of magnitude more sensitive to Sr2+ than skinned skeletal fibers. These results show that the affinity of cardiac TnC for Sr2+ is altered when substituted into skinned skeletal muscle fibers through protein-protein interactions.
D000818:Animals; D002118:Calcium / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D007700:Kinetics; D009119:Muscle Contraction; D009132:Muscles / Q000032:analysis*; D009206:Myocardium / Q000032:analysis; D015879:Myosin Subfragments / Q000378:metabolism; D011817:Rabbits; D013324:Strontium / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*; D019209:Troponin C
D015879:Myosin Subfragments; D014336:Troponin; D019209:Troponin C; D004492:Edetic Acid; D002118:Calcium; D013324:Strontium