Ca-dependent regulation of the subunit exchange of F-actin under the influence of tropomyosin and troponin.
A quasi-steady state rate of actin subunit incorporation into a complex of F-actin, tropomyosin, and troponin was studied in a solution containing MgCl2 0.5 mM, ATP 0.2 mM, Tris-HCl 5 mM (pH 8.0), and either CaCl2 64 muM or EGTA 644 muM at 33 degrees C by adding a small amount (less than 1 muM) of fluorescence-labeled actin monomer. Incorporation of the labeled actin monomer was remarkably much slower in the presence of EGTA, but the rate recovered instantaneously upon addition of an excess amount of CaCl2. The rate was very much reduced by the presence of cytochalasin D (1 muM) and again showed Ca-dependence.
D000199:Actins / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D055598:Chemical Phenomena; D002621:Chemistry; D007700:Kinetics; D008274:Magnesium; D015636:Magnesium Chloride; D012996:Solutions; D014335:Tropomyosin / Q000378:metabolism*; D014336:Troponin / Q000378:metabolism*
D000199:Actins; D012996:Solutions; D014335:Tropomyosin; D014336:Troponin; D015636:Magnesium Chloride; D008274:Magnesium; D002118:Calcium