1O1C: Molecular Models of Averaged Rigor Crossbridges From Tomograms of Insect Flight Muscle

Citation:
Abstract
Electron tomography, correspondence analysis, molecular model building, and real-space refinement provide detailed 3-D structures for in situ myosin crossbridges in the nucleotide-free state (rigor), thought to represent the end of the power stroke. Unaveraged tomograms from a 25-nm longitudinal section of insect flight muscle preserved native structural variation. Recurring crossbridge motifs that repeat every 38.7 nm along the actin filament were extracted from the tomogram and classified by correspondence analysis into 25 class averages, which improved the signal to noise ratio. Models based on the atomic structures of actin and of myosin subfragment 1 were rebuilt to fit 11 class averages. A real-space refinement procedure was applied to quantitatively fit the reconstructions and to minimize steric clashes between domains introduced during the fitting. These combined procedures show that no single myosin head structure can fit all the in situ crossbridges. The validity of the approach is supported by agreement of these atomic models with fluorescent probe data from vertebrate muscle as well as with data from regulatory light chain crosslinking between heads of smooth muscle heavy meromyosin when bound to actin.
PDB ID: 1O1CDownload
MMDB ID: 21304
PDB Deposition Date: 2002/11/18
Updated in MMDB: 2012/11 
Experimental Method:
electron microscopy
Resolution: 70  Å
Source Organism:
Oryctolagus cuniculus
Similar Structures:
Biological Unit for 1O1C: 29-meric; determined by author
Molecular Components in 1O1C
Label Count Molecule
Proteins (29 molecules)
5
Skeletal Muscle Myosin II
Molecule annotation
5
Skeletal Muscle Myosin II Regulatory Light Chain
Molecule annotation
5
Skeletal Muscle Myosin II Essential Light Chain
Molecule annotation
14
Skeletal Muscle Actin
Molecule annotation
* Click molecule labels to explore molecular sequence information.

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