Troponin isoform dependent pH dependence of the Ca(2+)-activated myofibrillar ATPase activity of avian slow and fast skeletal muscles.
The effects of acidic pH were examined on the Ca(2+)-sensitive ATPase activity of chicken fast and slow skeletal muscle myofibrils. In both types of myofibrils the Ca(2+)-sensitivity declined on decreasing pH from 7.4 to 6.2, but the slow skeletal muscle myofibrils were found to exhibit a Ca(2+)-sensitive ATPase activity which was more resistant to acidic pH compared to the fast skeletal muscle myofibrils. The results obtained by using a novel method for replacing whole troponin complex in myofibrils provide the first evidence that troponin is responsible for this higher resistibility of slow skeletal muscle myofibrils to acidosis.
Kawashima
A
A
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Morimoto
S
S
Suzuki
A
A
Shiraishi
F
F
Ohtsuki
I
I
D000818:Animals; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002645:Chickens; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D018656:Muscle Fibers, Fast-Twitch / Q000502:physiology; D018657:Muscle Fibers, Slow-Twitch / Q000502:physiology; D018482:Muscle, Skeletal / Q000201:enzymology*; D009210:Myofibrils / Q000201:enzymology*; D014336:Troponin / Q000032:analysis / Q000302:isolation & purification / Q000502:physiology*
D014336:Troponin; D000252:Calcium-Transporting ATPases