X-ray structures of the MgADP, MgATPγS, and MgAMPPNP complexes of the Dictyostelium discoideum myosin motor domain

摘要: The three-dimensional structures of the truncated myosin head from Dictyostelium discoideum myosin II (S1dC) complexed with MgAMPPNP, MgATPγS, and MgADP are reported at 2.1, 1.9, and 2.1 Å resolution, respectively. Crystals were obtained by cocrystallization and were isomorphous with respect to those of S1dC·MgADP·BeFx [Fisher, A. J., et al. (1995) Biochemistry 34, 8960−8972]. In all three structures, the electron density for the entire nucleotide was clearly discernible. The overall structures of all three complexes are very similar to that of the beryllium fluoride complex which suggests that the differences in the physiological effects of ATPγS and AMPPNP are due to the changes in the equilibrium between the actin-bound and actin-free states of myosin caused by the lower affinity of AMPPNP for myosin. In S1dC·MgAMPPNP, the presence of the bridging nitrogen prompts the side chain of Asn233 to rotate …