Related Experiment Video
Updated: Jul 24, 2026

Demonstrating the Uses of the Novel Gravitational Force Spectrometer to Stretch and Measure Fibrous Proteins
Published on: March 19, 2011
Coiled-coil unwinding at the smooth muscle myosin head-rod junction is required for optimal mechanical performance
A M Lauzon1, P M Fagnant, D M Warshaw
1Meakins-Christie Laboratories, McGill University Health Center, Montreal, Quebec H2X 2P2, Canada.
Abstract:
Myosin II has two heads that are joined together by an alpha-helical coiled-coil rod, which can separate in the region adjacent to the head-rod junction (Trybus, K. M. 1994. J. Biol. Chem. 269:20819-20822). To test whether this flexibility at the head-rod junction is important for the mechanical performance of myosin, we used the optical trap to measure the unitary displacements of heavy meromyosin constructs in which a stable coiled-coil sequence derived from the leucine zipper was introduced into the myosin rod. The zipper was positioned either immediately after the heads (0-hep zip) or following 15 heptads of native sequence (15-hep zip). The unitary displacement (d) decreased from d = 9.7 +/- 0.6 nm for wild-type heavy meromyosin (WT HMM) to d = 0.1 +/- 0.3 nm for the 0-hep zip construct (mean +/- SE). Native values were restored in the 15-hep zip construct (d = 7.5 +/- 0.7 nm). We conclude that flexibility at the myosin head-rod junction, which is provided by an unstable coiled-coil region, is essential for optimal mechanical performance.
Related Concept Videos
Overview of Myosin Structure and Function
Actin and Myosin in Muscle Contraction
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...
Structure and Organization of Smooth Muscles
Structure of smooth muscle cell
Smooth muscle cells are spindle-shaped with tapering ends and a...
Fascicle Arrangement in Skeletal Muscles
The four primary types of muscle based on fascicle arrangement are:
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...

