X-ray diffraction evidence for myosin-troponin connections and tropomyosin movement during stretch activation of insect flight muscle.

Published

Journal Article

Stretch activation is important in the mechanical properties of vertebrate cardiac muscle and essential to the flight muscles of most insects. Despite decades of investigation, the underlying molecular mechanism of stretch activation is unknown. We investigated the role of recently observed connections between myosin and troponin, called "troponin bridges," by analyzing real-time X-ray diffraction "movies" from sinusoidally stretch-activated Lethocerus muscles. Observed changes in X-ray reflections arising from myosin heads, actin filaments, troponin, and tropomyosin were consistent with the hypothesis that troponin bridges are the key agent of mechanical signal transduction. The time-resolved sequence of molecular changes suggests a mechanism for stretch activation, in which troponin bridges mechanically tug tropomyosin aside to relieve tropomyosin's steric blocking of myosin-actin binding. This enables subsequent force production, with cross-bridge targeting further enhanced by stretch-induced lattice compression and thick-filament twisting. Similar linkages may operate in other muscle systems, such as mammalian cardiac muscle, where stretch activation is thought to aid in cardiac ejection.

Full Text

Duke Authors

Cited Authors

  • Perz-Edwards, RJ; Irving, TC; Baumann, BAJ; Gore, D; Hutchinson, DC; Kržič, U; Porter, RL; Ward, AB; Reedy, MK

Published Date

  • January 4, 2011

Published In

Volume / Issue

  • 108 / 1

Start / End Page

  • 120 - 125

PubMed ID

  • 21148419

Pubmed Central ID

  • 21148419

Electronic International Standard Serial Number (EISSN)

  • 1091-6490

Digital Object Identifier (DOI)

  • 10.1073/pnas.1014599107

Language

  • eng

Conference Location

  • United States