Molecular modeling of averaged rigor crossbridges from tomograms of insect flight muscle.


Journal Article

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.

Full Text

Cited Authors

  • Chen, LF; Winkler, H; Reedy, MK; Reedy, MC; Taylor, KA

Published Date

  • April 2002

Published In

Volume / Issue

  • 138 / 1-2

Start / End Page

  • 92 - 104

PubMed ID

  • 12160705

Pubmed Central ID

  • 12160705

International Standard Serial Number (ISSN)

  • 1047-8477

Digital Object Identifier (DOI)

  • 10.1016/s1047-8477(02)00013-8


  • eng

Conference Location

  • United States