Related Experiment Video
Updated: Jul 28, 2026

Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
A 35-A movement of smooth muscle myosin on ADP release
M Whittaker1, E M Wilson-Kubalek, J E Smith
1Department of Cell Biology, Scripps Research Institute, La Jolla, California 92037, USA.
Abstract:
Myosin II crossbridges interact with F-actin producing powerstrokes of around 100 A (refs 1, 2), during which the products of ATP hydrolysis are released. This has been postulated to involve an articulation of the myosin head (S1) on actin, or substantial conformational changes in S1 itself. Small movements of the regulatory light chain have been detected (see, for example, refs 9, 10), but most data suggest that the bulk of S1 does not move on actin during crossbridge cycling. Here we present three-dimensional maps of S1-decorated F-actin in the presence and absence of MgADP. The myosin motor domain is similar in both states but there are major orientational differences in the light-chain-binding domain. This domain acts as a rigid level arm pivoting about the end of the motor domain and swinging approximately 23 degrees, resulting in a approximately 35-A step. Small, nucleotide-mediated conformational changes in the motor domain may thus be converted by the light-chain domain into large movement steps.
Related Concept Videos
Cross-bridge Cycle
Actin and Myosin in Muscle Contraction
The Movement of Organelles and Vesicles
Role of Myosin in Cell Migration
Myosin II is a hexamer comprising two heavy chains with globular heads and coiled-coil tails, two regulatory light chains, and two essential light chains. The ATPase sites on the myosin heads hydrolyze ATP, and the released phosphate generates the force for contraction. It is...
Excitation-Contraction Coupling in Skeletal Muscles
When an action potential...
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...

