Behavior of water molecules in ATPase pocket of myosin

Not a single water molecule but a group of water molecules frequently play an important role to functionalize the enzymatic reaction of proteins. In this study, we carried out molecular dynamics (MD) simulations for four types of myosin-nucleotide complexes; the ATP and/or ADP/Pi-bound myosins with the cleft open and/or close conformations. Computational results show a keen role of water molecules that are regulated by a salt-bridge formed between Arg238 in Switch I and Glu459 in Switch II. Before the ATP hydrolysis, Arg238 and Glu459 hold a lytic-water near ATP-γ phosphate and close the salt-bridge to inhibit any other water to enter the ATPase pocket except one water that controls the orientation of the lytic-water facing to ATP. Once the salt-bridge is opened after ATP hydrolysis, a large number of water molecules are circulating in the ATPase pocket. Our results demonstrate that the access of water molecules is precisely controlled in the respective reaction step of the ATP hydrolysis cycle.