[Interaction of phosphorylase kinase with thin filament proteins of rabbit skeletal muscles]

The binding of phosphorylase kinase to thin filaments and their effects on the enzyme activity as well as the contribution of the enzyme to contractile protein phosphorylation have been studied. The data obtained suggest that the kinase binding to thin filaments is controlled by the regulatory proteins, troponin and tropomyosin. The bulk of the enzyme is bound to the F-actin-tropomyosin-troponin complex which activates the enzyme in a far greater degree than each of its constituent components. Ca2+ and ATP control the kinase binding to F-actin. ATP increases the enzyme binding 6-fold; Ca2+ decrease the S0.5 value for F-actin 5-fold. In acetone powder extracts phosphorylase kinase phosphorylates thin filament-bound phosphorylase b, troponin T and troponin I as well as 51-58 kDa and 114 kDa proteins. These results suggest that phosphorylase kinase plays a role in the mechanism of synchronization of glycogenolysis and muscle contraction rates.