An X-Ray Diffraction Study on the ADP-Induced Conformational Change in Skeletal Muscle Myosin

Abstract

Effects of ADP on the conformation of myosin cross-bridges were studied in x-ray diffraction experiments on single skinned fibers of frog skeletal muscle by photorelease of ADP from caged-ADP. The experiments were performed at the third-generation synchrotron radiation facility SPring-8 with a time resolution of 5ms. The intensity of the third-order meridional reflection from myosin filaments (at 1/14.4 nm^-1) increased promptly after the ADP release with a time constant smaller than 5ms, which was similar to that of tension decline. The results show that ADP binding induces a conformational change of myosin in skeletal muscle fibers.