Related Experiment Video
Updated: Aug 17, 2026

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
Published on: May 4, 2022
Evidence against essential roles for subdomain 1 of actin in actomyosin sliding movements
Md Shahjahan P Siddique1, Takashi Miyazaki, Eisaku Katayama
1Department of Materials Processing, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579, Japan.
Abstract:
We have engineered acto-S1chimera proteins carrying the entire actin inserted in loop 2 of the motor domain of Dictyostelium myosin II with 24 or 18 residue-linkers (CP24 and CP18, respectively). These proteins were capable of self-polymerization as well as copolymerization with skeletal actin and exhibited rigor-like structures. The MgATPase rate of CP24-skeletal actin copolymer was 1.06 s(-1), which is slightly less than the V(max) of Dictyostelium S1. Homopolymer filaments of skeletal actin, CP24, and CP18 moved at 4.7+/-0.6, 2.9+/-0.6, and 4.1+/-0.8 microm/s (mean+/-SD), respectively, on coverslips coated with skeletal myosin at 27 degrees C. Statistically thermodynamic considerations suggest that the S1 portion of chimera protein mostly resides on subdomain 1 (SD-1) of the actin portion even in the presence of ATP. This and the fact that filaments of CP18 with shorter linkers moved faster than CP24 filaments suggest that SD-1 might not be as essential as conventionally presumed for actomyosin sliding interactions.
Related Concept Videos
The Role of Actin and Myosin in Non-muscle Cells
Actin Filament Depolymerization
In F-actin, the ADF/cofilin proteins...
Generation of Straight or Branched Actin Filaments
Arp2/3 Complex
Arp2/3 complex is a seven-subunit complex consisting of two proteins similar to actin- Arp2 and Arp3, and five other subunits that help keep Arp2 and Arp3 inactive. When required, the complex is...
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...
Actin and Myosin in Muscle Contraction
Introduction to Actin

