Abstract
Utilizing quick-freeze deep-etch-replica electron-microscopy, we observed that actin-attached myosin during in vitro sliding was oppositely-bent, considering the direction of the putative pre-power stroke configuration. Since SH1–SH2-cross-linked myosin was a good candidate with a similar appearance, we devised a new procedure to define the relative angle of the catalytic-domain and the lever-arm from the averaged images, and built its 3-D model. The projection angle of the lever-arm in that model was compatible with actin-sliding cross-bridge structure. Introducing this conformer as the structural analogue of the transient intermediate, we propose a revised scheme of the crossbridge-cycle compatible with various experimental results.
