Document Type

Article

Publication Date

2016

DOI

10.1016/j.jmb.2016.01.027

Publication Title

Journal of Molecular Biology

Volume

428

Issue

6

Pages

1142-1164

Abstract

Tarantula striated muscle is an outstanding system for understanding the molecular organization of myosin filaments. Three-dimensional reconstruction based on cryo-electron microscopy images and single-particle image processing revealed that, in a relaxed state, myosin molecules undergo intramolecular head head interactions, explaining why head activity switches off. The filament model obtained by rigidly docking a chicken smooth muscle myosin structure to the reconstruction was improved by flexibly fitting an atomic model built by mixing structures from different species to a tilt-corrected 2-nm three-dimensional map of frozen-hydrated tarantula thick filament. We used heavy and light chain sequences from tarantula myosin to build a single-species homology model of two heavy meromyosin interacting-heads motifs (IHMs). The flexibly fitted model includes previously missing loops and shows five intramolecular and five intermolecular interactions that keep the IHM in a compact off structure, forming four helical tracks of IHMs around the backbone. The residues involved in these interactions are oppositely charged, and their sequence conservation suggests that IHM is present across animal species. The new model, PDB 3JBH, explains the structural origin of the ATP turnover rates detected in relaxed tarantula muscle by ascribing the very slow rate to docked unphosphorylated heads, the slow rate to phosphorylated docked heads, and the fast rate to phosphorylated undocked heads. The conservation of intramolecular interactions across animal species and the presence of IHM in bilaterians suggest that a super-relaxed state should be maintained, as it plays a role in saving ATP in skeletal, cardiac, and smooth muscles.

Comments

NOTE: This is the author's pre-print version of a work that was published in Journal of Molecular Biology. The final version was published as:

Alamo, L., Qi, D., Wriggers, W., Pinto, A., Zhu, J. G., Bilbao, A., . . . Padron, R. (2016). Conserved intramolecular interactions maintain myosin interacting-heads motifs explaining tarantula muscle super-relaxed state structural basis. Journal of Molecular Biology, 428(6), 1142-1164. doi:10.1016/j.jmb.2016.01.027

Available at: http://dx.doi.org/10.1016/j.jmb.2016.01.027

Original Publication Citation

Alamo, L., Qi, D., Wriggers, W., Pinto, A., Zhu, J. G., Bilbao, A., . . . Padron, R. (2016). Conserved intramolecular interactions maintain myosin interacting-heads motifs explaining tarantula muscle super-relaxed state structural basis. Journal of Molecular Biology, 428(6), 1142-1164. doi:10.1016/j.jmb.2016.01.027

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