Abstract: Objective: The objective of this study was to investigate the regulation of actomyosin dissociation and ATPase activity in crude actomyosin extract by changing the phosphorylation level of actomyosin. Methods: The crude actomyosin extract was incubated with protein kinase A and alkaline phosphatase at 4 ℃ for 48 h. Subsequently, the changes in protein phosphorylation, actomyosin dissociation and ATPase activity were measured by SDS-PAGE, Pro-Q Diamond phosphoprotein gel staining kit, Western blotting and ATPase activity assay kit. Results: The phosphorylation levels of troponin T (TnT) and myosin regulatory light chain (MRLC) were significantly higher in the protein kinase A group compared with the control group. The amount of liberated actin in the protein kinase A group was significantly higher than that in control group, and it increased significantly during the first two hours and increased slightly during the following 46 hours in both groups. In addition, the actomyosin ATPase activity decreased significantly in the protein kinase A group compared with the control group, and it increased significantly with incubation time in the two groups. However, the opposite changes were observed for the alkaline phosphatase group. Conclusion: The phosphorylation of TnT and MRLC reduces the binding force between myosin and actin and thereby promotes the dissociation of actomyosin.

Key words: phosphorylation, myosin regulatory light chain, troponin T, actomyosin dissociation