Role of troponin C in determining the Ca(2+)-sensitivity and cooperativity of the tension development in rabbit skeletal and cardiac muscles.
The role of troponin C in determining the characteristic differences in contraction between fast-twitch skeletal and cardiac muscles was investigated with rabbit skinned psoas fibers and left ventricular trabeculae by exchanging their troponins C using a technique involving extraction and replacement. In both muscle types, skeletal troponin C conferred higher cooperativity on the Ca(2+)-activated tension development than cardiac troponin C, indicating that troponin C plays a crucial role in determining the cooperativity in Ca2+ activation of vertebrate striated muscle. Furthermore, the foreign type of troponin C was found to confer lower Ca2+ sensitivity on the tension development in both fast-twitch skeletal and cardiac muscles than the native type of troponin C. This indicates that the Ca2+ sensitivity of each muscle type is determined by troponin C interactions with other troponin subunits and not by troponin C alone.
Morimoto
S
S
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka.
Ohtsuki
I
I
D000494:Allosteric Regulation; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002135:Calcium-Binding Proteins / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000502:physiology*; D009132:Muscles / Q000378:metabolism; D009200:Myocardial Contraction / Q000502:physiology*; D009206:Myocardium / Q000378:metabolism; D011817:Rabbits; D013552:Swine; D014336:Troponin / Q000502:physiology*; D019209:Troponin C
D002135:Calcium-Binding Proteins; D014336:Troponin; D019209:Troponin C; D002118:Calcium