Helical order in myosin filaments and evidence for one ligand inducing multiple myosin conformations.

The basic processes of muscle contraction are well understood: it is a result of cyclic interactions between myosin and actin, driven by the energy of ATP hydrolysis. Since the availability of the crystal structures of the contractile proteins, and with the advent of single molecule assays, the field has made great strides in understanding the underlying processes. However, the details of the mechanism of transduction of chemical to mechanical energy still remain largely unresolved. One of the obstacles is that most of the studies at the molecular level are based on isolated, in vitro systems, e.g. the atomic structure of the myosin head is known but not its complex with actin and EM reconstruction is based on isolated filaments. The link between the information obtained from the in vitro systems and the actual processes occurring in intact muscle is still largely missing. The aim of our efforts is to provide such a link.