Electron tomography of insect flight muscle in rigor and AMPPNP at 23 degrees C

Journal of Molecular Biology
H SchmitzK A Taylor

Abstract

Treatment of rigor fibers of insect flight muscle (IFM) with AMPPNP at 23 degrees C causes a 70% drop in tension with little change in stiffness. In order to visualize the changes in crossbridge conformation and distribution that give rise to the mechanical response, we have produced three-dimensional reconstructions by tomography of both rigor and AMPPNP-treated muscle that do not average the repeating motifs of crossbridges, and thereby retain information on variability of crossbridge structure and distribution. Tomograms can be averaged when display of only the regular features is wanted. Tomograms of rigor IFM show double-headed lead and single-headed rear crossbridges. Tomograms of IFM treated with AMPPNP at 23 degrees C reveal many double-headed and some single-headed "lead" bridges but few crossbridges corresponding to the rear bridges of rigor. Instead, new non-rigor forms of variably angled crossbridges are found bound to actin sites not labeled with myosin heads in rigor. This indicates that the rear bridges of rigor have redistributed during the transition from rigor to the AMPPNP state, which could explain the maintenance of rigor stiffness despite the loss of tension. Comparison of in situ crossbridges in tomograms...Continue Reading

Citations

Jun 15, 2005·Annual Review of Biochemistry·Vladan LucićWolfgang Baumeister
May 17, 2003·Proceedings of the National Academy of Sciences of the United States of America·Walter SteffenJohn Sleep
Apr 25, 2002·Proceedings of the National Academy of Sciences of the United States of America·Tania ChakrabartyPaul R Selvin
Nov 14, 1997·The Journal of Cell Biology·S A BurgessJ Trinick
Jun 23, 2019·The Journal of General Physiology·Yahor SavichDavid D Thomas
Apr 10, 2019·International Journal of Molecular Sciences·Kenneth A TaylorMichael K Reedy
Jun 3, 2015·Cytoskeleton·William M SchmidtJeffrey R Moore
Jun 10, 1998·Journal of Structural Biology·T Walz, N Grigorieff
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Jan 30, 2004·Biophysical Journal·Hunter MartinRobert J Barsotti

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