@article{8,
  keywords = {Adenosine Triphosphate, Animals, Dictyostelium, Myosins, Actins, Adenosine Triphosphatases, Electrochemistry, Nucleotides, Protein Conformation},
  author = {C Murphy and J Spudich},
  title = {The sequence of the myosin 50-20K loop affects Myosin{\textquoteright}s affinity for actin throughout the actin-myosin ATPase cycle and its maximum ATPase activity.},
  abstract = { <p>We are interested in the role that solvent-exposed, proteolytically sensitive surface loops play in myosin function. The 25-50K loop, or loop 1, is near the ATP binding site, while the 50-20K loop (loop 2) is in the actin binding site. Through chimeric studies, we have found that loop 1 affects ADP release [Murphy, C. T., and Spudich, J. A. (1998) Biochemistry 37, 6738-44], while loop 2 affects the actin-activated ATPase activity [Uyeda, T. Q.-P., et al. (1994) Nature 368, 567-9]. In the study described here, we have found that the kcat of the actin-activated ATPase activity is changed by the loop 2 substitutions in a manner that reflects the relative actin-activated ATPase activities of the donor myosins. Additionally, changes in loop 2 affect the affinity of myosin for actin both in the presence and in the absence of nucleotides. Pre-steady-state studies together with the ATPase and affinity data suggest that while loop 2 does not affect interactions between myosin and nucleotide, it plays a role in determining the affinity of myosin for actin in various nucleotide states and in the rate-limiting transition allowing phosphate release.</p>
 },
  year = {1999},
  journal = {Biochemistry},
  volume = {38},
  pages = {3785-92},
  month = {1999 Mar 23},
  issn = {0006-2960},
  doi = {10.1021/bi9826815},
  language = {eng},
}