STRUCTURE OF THE MYOSIN HEAD IN SOLUTION AND THE EFFECT OF LIGHT CHAIN-2 REMOVAL

Structural properties of rabbit skeletal myosin head (Sl) and the influence of the DTNB light chain (LC2) on the size and shape of myosin heads in solution were investigated by small angle x-ray scattering. The LC2 deficient myosin head, Sl (-LC2), and the S1 containing LC2 light chain, Sl (+LC2) were studied in parallel. The respective values of the radius of gyration were found to be (40.2 +/- 0.5) angstrom and (46.7 +/- 1) angstrom, while the maximum dimension was (190 +/- 15) angstrom for both species. The large difference between the two R(g) values suggest that LC2 is located close to one extremity of the myosin head, in agreement with most electron microscopy observations. All models derived from the x-ray scattering pattern of the native myosin head share a common overall morphology, showing two main regions, an asymmetric globular portion which tapers smoothly into a thinner domain of roughly equivalent length making an angle of approximately 60-degrees, with a contour length of approximately 210 angstrom.