Disassembly and reconstitution of the Ca2+-sensitive thin filaments of vascular smooth muscle.
The Ca2+-sensitive thin filaments of aorta smooth muscle have been, disassembled into their constituent proteins, actin, tropomyosin and a 120-kDa protein. The 120-kDa protein bound to aorta actin-tropomyosin and inhibited its ability to activate myosin MgATPase. This inhibition correlated with the binding of one 120-kDa protein molecule per 29 actin monomers. Upon the addition of calmodulin to the actin-tropomyosin-120-kDa protein complex, the inhibition was relieved in 10(-4) M Ca2+ but not 10(-9) M Ca2+. The full release of inhibition was not accompanied by a full release of 120-kDa protein binding to actin-tropomyosin. A fully active, Ca2+-sensitive aorta thin filament has thus been reconstituted from just four components: actin, tropomyosin, 120-kDa protein and calmodulin.
D000199:Actins / Q000502:physiology; D000818:Animals; D001011:Aorta / Q000032:analysis; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology; D009124:Muscle Proteins / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000032:analysis / Q000378:metabolism*; D012756:Sheep; D014335:Tropomyosin / Q000502:physiology
D000199:Actins; D002147:Calmodulin; D009124:Muscle Proteins; D014335:Tropomyosin; D002118:Calcium