Real Space Refinement of Acto-myosin Structures from Sectioned Muscle

Electron Tomography of Swollen Rigor Fibers of Insect Flight Muscle Reveals a Short and Variably Angled S2 Domain

“…33,47 The improvement brings out details of the actin filament, but also reveals a significant negative stain component in the images, which appears as a surface shell of stain enclosing the myosin motor domains and the thick and thin filaments. The shell was not readily apparent over either the lever arm or the S2 domain.…”

Electron tomography of fast frozen, stretched rigor fibers reveals elastic distortions in the myosin crossbridges

“…Improvements in the resolution of the class averages utilize a modification of multireference image alignment and hierarchical ascendant classification (Chen et al, 2001;Winkler and Taylor, 1999). Individual crossbridge motifs are repeating units of the tomogram containing a 38.7 nm length of the thin filament that includes one-half turn of the actin helix, the crossbridges bound to actin and a portion of the flanking thick filaments from which the crossbridges originate.…”

“…Correspondence analysis was first applied to chemically fixed IFM in rigor (Chen et al, 2001(Chen et al, , 2002, a stable, well-ordered state that has been extensively characterized by electron microscopy (Reedy and Reedy, 1985;Reedy et al, 1965;Schmitz et al, 1996;Taylor et al, 1989Taylor et al, , 1993) and X-ray fiber diffraction (Holmes et al, 1980). In rigor, the maximum possible number of myosin heads form long lasting actin attachments, frequently binding by both heads of one molecule to form one crossbridge.…”

Invertebrate muscles: Thin and thick filament structure; molecular basis of contraction and its regulation, catch and asynchronous muscle

“…Techniques for identifying, averaging, and extracting three-dimensional information from the repeating motifs present in electron micrographs {Al Khayat, 2004 37678 /id; 23274 /id} and of X-ray diffraction patterns (Squire et al, 2003a) of asynchronous muscle are well-developed. Structural modeling began early in asynchronous muscle studies (Holmes et al, 1982), and protocols for fitting atomic models of actin and myosin head and neck regions to cross-bridge images are now also well-developed (Chen et al, 2001). Asynchronous muscle has been studied in four states: rigor, semi-relaxed by the addition of non-hydrolyzable ATP analogs or similar treatments, relaxed, and actively contracting.…”