1. A Structuralist's View of Muscle Contraction K.C. HOLMES, Max-Planck Institute for Medical Research, Heidelberg, Germany
The structures of a truncated form (without the lever arm) of Dictyostelium discoideum (slime mold) myosin 2 motor domain have been elucidated by Rayment's lab with a variety of nucleotide analogues bound in the active site. Dominguez et al. have obtained similar results with smooth muscle myosin (for review see Geeves and Holmes. 1999. Annu. Rev. Biochem. 68:687–728). These studies reveal the occurrence of two conformations of myosin (OPEN and CLOSED active site) entailing a movement of 5–6 Å of the switch 2 region. This movement is coupled with a large movement of the converter domain (a 60° rotation). CLOSED may only be stable in the presence of the γ-phosphate. Truncated Dictyostelium myosin 2 with ADP.BeF3 in the active site was found by Rayment et al. to be in the OPEN form....
