Replacement of troponin components in myofibrils.
The Ca(2+)-sensitive ATPase activity of rabbit skeletal myofibrils was desensitized by treatment with excess troponin T and was found to be activated irrespective of the Ca2+ concentrations. A SDS-gel electrophoretic study showed that both troponin C and troponin I were removed from the myofibrils on treatment with troponin T. The Ca(2+)- and Sr(2+)- sensitivities of the ATPase of troponin T-treated myofibrils reconstituted with troponin C. I were the same as in the intact myofibrils. The Ca(2+)-activated ATPase of rabbit skeletal myofibrils was also desensitized on treatment with chicken breast troponin T or its 26K fragment. The SDS-gel electrophoretic study revealed that troponin T, in addition to troponin C and troponin I, was also removed from the myofibrils and, instead, chicken breast troponin T or its 26K fragment was incorporated into the myofibrils. The Ca(2+)- sensitivity of myofibrils treated with chicken breast troponin T or its 26K fragment was then regained on reconstitution with troponin C.I. These findings indicate that the change in composition of myofibrils on treatment with troponin T or its 26K fragment is due to the selective replacement of the troponin C.I.T complex in the myofibrils as a whole with troponin T or its 26K fragment.
Shiraishi
F
F
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka.
Kambara
M
M
Ohtsuki
I
I
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002645:Chickens; D004586:Electrophoresis; D009210:Myofibrils / Q000737:chemistry* / Q000201:enzymology; D011817:Rabbits; D013324:Strontium / Q000494:pharmacology; D014336:Troponin / Q000737:chemistry* / Q000494:pharmacology; D019209:Troponin C; D019210:Troponin I; D020107:Troponin T
D014336:Troponin; D019209:Troponin C; D019210:Troponin I; D020107:Troponin T; D000252:Calcium-Transporting ATPases; D002118:Calcium; D013324:Strontium