Molecular Dynamics of Vertebrate Muscle Thick and Thin Filaments

摘要

Myosin-containing thick and actin-containing thin filaments generate force in vertebrate muscles. In an effort to monitor molecular dynamics and its relation to function in these filaments, we have labeled sulfhydryls actin (cys-374) and mysoin (SH1) with the triplet probe erythrosin-5-iodoacetamide. Fluorescence studies indicate that the probes are rigidly bound to the proteins and (probably) associated with the protein surface. Although the probe phosphorescence in solution is always mono-exponential, in the protein conjugates the decays are mono-exponential for actin but multi-exponential for myosin at 20°C. The steady-state anisotropy (averaged over the time window from 0.07 to 1.5ms) of erythrosin-labeled G-actin is 0.0; in F-actin the anisotropy is 0.088 at 20°C and increases to 0.10 when the peptide toxin phalloidin, which is known to stabilize F-actin filaments, is bound.