Related Experiment Video
Updated: Jul 16, 2026

Optogenetic Inhibition of Rho1-Mediated Actomyosin Contractility Coupled with Measurement of Epithelial Tension in Drosophila Embryos
Published on: April 14, 2023
Caldesmon inhibits both force development and transition of actin monomers from "OFF" to "ON" conformational state by
Olga E Pronina1, Robert Makuch, Antoni Wrzosek
1Laboratory of Mechanisms of Cell Motility, Institute of Cytology, Russian Academy of Sciences, 4 Tikhoretsky Avenue, St. Petersburg 194064, Russia.
Abstract:
We have investigated the effect of caldesmon on the actin conformational state and its position at force generation in glycerinated fibers upon transformation from relaxation to rigor. F-actin and caldesmon were labeled with TRITC-phalloidin or acrylodan, respectively, and the orientation and mobility of the probes were calculated. Transition from relaxation to rigor was accompanied by force development and by the changes in orientation and mobility of TRITC-phalloidin that were typical for actin monomer transformation from the "OFF" to the "ON" conformational state. In the presence of caldesmon, both the force developed by the fibers and the changes in the orientation and mobility of TRITC-phalloidin were markedly decreased. In contrast, the orientation and mobility of acrylodan change essentially showed the displacement of the caldesmon molecules and the changes in its mobility. The results are evidence that structure and/or mode of the attachment of caldesmon to actin modulates both the force production and transition of actin monomers from "OFF" to "ON" conformations in the ATPase cycle.
Related Concept Videos
Actin Filament Depolymerization
In F-actin, the ADF/cofilin proteins...
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
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...
Actin Treadmilling
Actin and Myosin in Muscle Contraction
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...

