The Structure of the Actin-Smooth Muscle Myosin Motor Domain Complex in the Rigor State

Publication date: Available online 14 October 2017 Source:Journal of Structural Biology Author(s): Chaity Banerjee, Zhongjun Hu, Zhong Huang, J. Anthony Warrington, Dianne W. Taylor, Kathleen M. Trybus, Susan Lowey, Kenneth A. Taylor Myosin-based motility utilizes catalysis of ATP to drive the relative sliding of F-actin and myosin. The earliest detailed model based on cryo-electron microscopy (cryoEM) and X-ray crystallography postulated that higher actin affinity and lever arm movement were coupled to closure of a feature of the myosin head dubbed the actin-binding cleft. Several studies since then using crystallography of myosin-V and cryoEM structures of F-actin bound myosin-I, –II and –V have provided details of this model. The smooth muscle myosin II interaction with F-actin may differ from those for striated and non-muscle myosin II due in part to different lengths of important surface loops. Here we report a ∼6 Å resolution reconstruction of F-actin decorated with the nucleotide-free recombinant smooth muscle myosin-II motor domain (MD) from images recorded using a direct electron detector. Resolution is highest for F-actin and the actin-myosin interface (3.5-4 Å) and lowest (∼6-7 Å) for those parts of the MD at the highest radius. Atomic models built into the F-actin density are quite comparable to those previously reported for rabbit muscle actin and show density from the bound ADP. The atomic model of the MD, is quite similar to a recently publ...

Source: Journal of Structural Biology - October 14, 2017 Category: Biology Source Type: research