Calcium/calmodulin regulation of ATPase activity and endogenous phosphorylation of mammalian brain actomyosin.
Rabbit brain actomyosin showed several fold stimulation of the MgATPase activity by Ca2+ alone and by Ca2+/calmodulin. The calmodulin-binding drug, fluphenazine, abolished the stimulated activity. In the presence of Ca2+, exogenous calmodulin had a biphasic effect on ATPase activity at low concentrations (less than 0.15 microM) and activated the ATPase activity by 60-70% at about 1 microM. Tropomyosin-troponin complex from skeletal muscle did not stimulate the ATPase activity of brain actomyosin, but conferred Ca2+ sensitivity to a skeletal muscle myosin/brain actomyosin mixture. These results indicate the presence of myosin-linked, calmodulin-dependent, Ca2+-regulatory system for brain actomyosin. Heavy and light chains of brain myosin were found to be rapidly phosphorylated by endogenous Ca2+-dependent protein kinase(s). Ca2+-independent phosphorylation of one of the light chains was also observed.
D000205:Actomyosin / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000378:metabolism*; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology*; D002147:Calmodulin / Q000494:pharmacology*; D002417:Cattle; D005476:Fluphenazine / Q000494:pharmacology; D007700:Kinetics; D010766:Phosphorylation; D014335:Tropomyosin / Q000378:metabolism; D014336:Troponin / Q000378:metabolism
D002147:Calmodulin; D014335:Tropomyosin; D014336:Troponin; D000205:Actomyosin; D017301:Ca(2+) Mg(2+)-ATPase; D005476:Fluphenazine; D002118:Calcium