Key Points
- To resolve the molecular arrangement and helical symmetry of myosin cross-bridges on thick filaments isolated from Limulus telson muscle.
- Rapidly and gently isolated intact, long thick filaments (> 4.0 µm) from fresh, unstimulated Limulus telson muscle via an improved preparation protocol.
- Examined negatively stained filaments using transmission electron microscopy combined with optical diffraction analysis of the micrographs.
- Micrographs displayed highly periodic filaments with well-preserved myosin cross-bridge arrays matching a 43.8 nm helical repeat.
- Optical diffraction patterns confirmed a structural model featuring a four-stranded helix with 12 cross-bridges per turn and an axial repeat every third cross-bridge level (43.8 nm).
Structured PICO
PPopulationFresh, unstimulated Limulus telson muscle thick filaments
IInterventionElectron microscopy and optical diffraction analysis
OOutcomeStructure and arrangement of myosin cross-bridges and helical repeatsurrogate
This basic science study provides a detailed structural model for Limulus muscle thick filaments, demonstrating a four-stranded helical arrangement of myosin cross-bridges.