Fig. 7.
Comparison of the proton transfer rings among various ATP hydrolysis proteins. The proton transfer rings and the constituting mediators of the ATP hydrolysis reactions of (A) F-form actin, compared with some motor proteins, (B) myosin (32), (C) F1-ATPase (29), and (D) kinesin (30). Note that in F-form actin the mediators are W1 and W2, whereas the other three have additional mediators (indicated in red). Moreover, F1-ATPase and kinesin have multistep proton transfer strategies via the transient protonation of the glutamate side chains. The curved arrows in light blue indicate the directions and paths of proton transfer, and the dashed lines are hydrogen bonds.