Caldesmon specifically inhibits the effect of tropomyosin on actomyosin system in platelet.
Caldesmon, a calmodulin and actin binding protein, has been shown to exist in platelet. In this report, it is shown that caldesmon specifically inhibits the effect of tropomyosin to enhance the actomyosin ATPase activity in platelet. Platelet tropomyosin enhances the MgATPase activity of platelet actomyosin. This effect is abolished by platelet caldesmon. In the absence of tropomyosin, however, caldesmon has no effect on the ATPase activity. The inhibition is not due to displacement of the binding of tropomyosin to F-actin by caldesmon. The result indicates that caldesmon is the specific inhibitor of tropomyosin in resting platelet.
D000199:Actins / Q000097:blood; D000205:Actomyosin / Q000097:blood*; D000251:Adenosine Triphosphatases / Q000037:antagonists & inhibitors / Q000097:blood*; D000818:Animals; D001792:Blood Platelets / Q000502:physiology*; D002148:Calmodulin-Binding Proteins / Q000097:blood / Q000494:pharmacology*; D013552:Swine; D014335:Tropomyosin / Q000037:antagonists & inhibitors*
D000199:Actins; D002148:Calmodulin-Binding Proteins; D014335:Tropomyosin; D000205:Actomyosin; D000251:Adenosine Triphosphatases