title: Skeletal muscle myosin subfragment 1 dimers.
abstract: The rate of translational diffusion of skeletal muscle myosin subfragment 1 (S1) was determined from polarized dynamic light scattering autocorrelation measurements. Diffusion rates were expressed in terms of the hydrodynamic radii Rh. At 20 degrees C, in low ionic strength pH 8 solutions, Rh increased from 4.3 nm to 5.7 nm as [S1] was increased from 1.6 to 72 microM. Including MgATP to maintain S1. MgADP. Pi gave equivalent results. When the light scattering data were analyzed, assuming a monomer-dimer equilibrium, a dissociation constant of 83 microM was obtained. Steady state MgATPase activity measurements were made as a function of [ATP] for S1 in the 0.4-7 microM range, and analyzed assuming Michaelis-Menten kinetics. VMAX did not change, but KM increased about tenfold as [S1] was increased over this range. The light scattering and kinetic data were consistent with S1 aggregation at high [S1].
authors.affiliation: Department of Chemistry, Stanford University, CA 94305, USA.
authors.forename: K
authors.initials: K
authors.lastname: Claire
authors.forename: R
authors.initials: R
authors.lastname: Pecora
authors.forename: S
authors.initials: S
authors.lastname: Highsmith
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017301:Ca(2+) Mg(2+)-ATPase / Q000378:metabolism; D004058:Diffusion; D007700:Kinetics; D008027:Light; D018482:Muscle, Skeletal / Q000737:chemistry / Q000201:enzymology / Q000378:metabolism*; D015879:Myosin Subfragments / Q000737:chemistry / Q000378:metabolism*; D011817:Rabbits; D012542:Scattering, Radiation
chemical_list: D015879:Myosin Subfragments; D000255:Adenosine Triphosphate; D017301:Ca(2+) Mg(2+)-ATPase