Related Experiment Video
Updated: Dec 29, 2025

Probing Myosin Ensemble Mechanics in Actin Filament Bundles Using Optical Tweezers
Published on: May 4, 2022
Calmodulin bridging of IQ motifs in myosin-V
Stephen R Martin1, Peter M Bayley
1Division of Physical Biochemistry, National Institute for Medical Research, Mill Hill, London NW7 1AA, UK.
Abstract:
Ca(2+)-saturated calmodulin binds to double-length IQ lever-arm sequences from murine myosin-V, forming a 1:1 "bridging" complex with very high affinity, (K9d)<10 pM for double motifs, IQ34, IQ45 and IQ56). Such a 1:1 complex involves interaction of one calmodulin (CaM) molecule with two adjacent IQ-motifs, providing a molecular mechanism for the observed Ca(2+)-dependent CaM dissociation from the IQ-region. Structural considerations suggest that formation of the 1:1 complex requires a severe distortion of the lever-arm, potentially regulating functional motility. This would be consistent with a recent report of diverse, irregular shapes of the lever arm of myosin-V induced by the presence of Ca(2+).
Related Concept Videos
Cross-bridge Cycle
Overview of Myosin Structure and Function
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 and Myosin in Muscle Contraction
The Sarcomere
Each...

