Functional transitions in myosin: role of highly conserved Gly and Glu residues in the active site.

It has been proposed from crystallographic comparisons [Fisher, A. J., Smith, C. A., Thoden, J. B., Smith, R., Sutoh, K., Holden, H. M., & Rayment, I. (1995) Biochemistry 34, 8960-8972] that in one of the important transitions of myosin head (M), M x ATP --> M x ADP x Pi, a rotation occurs in Gly468 (of chicken smooth muscle myosin). We find that mutation of this Gly to Ala does block the transition. Searching for proton acceptors in ATPase catalysis, we also find that mutation of a candidate (Glu470 of chicken smooth muscle myosin) blocks the transition. Interpretations of both findings are examined.