The effect of troponin C substitution on the Ca(2+)-sensitive ATPase activity of vertebrate and invertebrate myofibrils by troponin Cs with various numbers of Ca(2+)-binding sites.
The effect of four different classes of troponin C with different numbers of Ca(2+)-binding sites was investigated on the Ca(2+)-activation profiles of the ATPase of troponin C-depleted myofibrils prepared from vertebrate fast skeletal (rabbit), vertebrate cardiac (bovine) and invertebrate crustacean tail striated (crayfish, lobster) muscles. Troponin C from vertebrate sources [fast skeletal (rabbit, chicken) with four Ca(2+)-binding sites, and cardiac (bovine, chicken) with three Ca(2+)-binding sites] activated the Ca(2+)-ATPase of troponin C-depleted myofibrils from the vertebrate skeletal or cardiac muscles, but did not activate the invertebrate troponin C-depleted crustacean myofibrils. On the other hand, two kinds of crustacean (crayfish, lobster) troponin C with two Ca(2+)-binding sites activated only crustacean troponin C-depleted myofibrils. One invertebrate molluscan (Akazara scallop) troponin C with one Ca(2+)-binding site did not activate the Ca(2+)-ATPase of the troponin C-depleted myofibrils from either vertebrate or crustacean striated muscles. The results obtained from the four kinds of combinations of troponin C and troponin C-depleted myofibrils from vertebrate skeletal and cardiac muscles demonstrated that the characteristic cooperativity of the Ca(2+)-activation profiles of both vertebrate skeletal and cardiac myofibrils was determined by the skeletal or cardiac origin of troponin C molecules, irrespective of the animal species, and the Ca(2+)-affinity of the myofibrillar ATPase was related to the skeletal or cardiac origin of both the troponin C and myofibrils. These findings indicated that each of the four classes of troponin C has its own characteristic Ca(2+)-activation profile for each kind of myofibril examined in the present study.
Nakamura
Y
Y
Department of Pharmacology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Shiraishi
F
F
Ohtsuki
I
I
D000818:Animals; D003400:Astacoidea; D001665:Binding Sites; D000252:Calcium-Transporting ATPases / Q000378:metabolism*; D002417:Cattle; D002614:Chelating Agents / Q000494:pharmacology; D004492:Edetic Acid / Q000031:analogs & derivatives; D066298:In Vitro Techniques; D008974:Mollusca; D009132:Muscles / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009210:Myofibrils / Q000187:drug effects / Q000378:metabolism*; D008121:Nephropidae; D011817:Rabbits; D013045:Species Specificity; D014336:Troponin / Q000145:classification / Q000378:metabolism*; D019209:Troponin C
D002614:Chelating Agents; D014336:Troponin; D019209:Troponin C; C005390:CDTA; D004492:Edetic Acid; D000252:Calcium-Transporting ATPases