previous studies had led to the conclusion that the globular , single-headed myosins ia and ib from acanthamoeba castellanii contain two actin-binding sites : one associated with the catalytic site and whose binding to f-actin activates the mg2+-atpase activity and a second site whose binding results in the cross-linking of actin filaments and makes the actin-activated atpase activity positively cooperative with respect to myosin i concentration .
C0025979
actin filaments
C0001271
actin