Actomyosin: law and order in motility

The crystal structures of smooth muscle and scallop striated muscle myosin have both been completed in the past 18 months. Structural studies of uncon ventional myosins, in particular the stunning discovery that myosin VI move s backwards on actin, are starting to have deep impact on the field and hav e induced new ways of thinking about actin-based motility. Sophisticated ge netic, biochemical and biophysical studies were used to test and refine hyp otheses of the molecular mechanism of motility that were developed in the p ast. Although all these studies confirmed some aspects of these hypotheses, they also raised many new unresolved questions. Much of the evidence point s to the importance of the actin-myosin binding process and an associated d isorder-to-order transition.