3DTP: Tarantula Heavy Meromyosin Obtained By Flexible Docking To Tarantula Muscle Thick Filament Cryo-em 3d-map

Citation:
Abstract
Muscle contraction involves the interaction of the myosin heads of the thick filaments with actin subunits of the thin filaments. Relaxation occurs when this interaction is blocked by molecular switches on these filaments. In many muscles, myosin-linked regulation involves phosphorylation of the myosin regulatory light chains (RLCs). Electron microscopy of vertebrate smooth muscle myosin molecules (regulated by phosphorylation) has provided insight into the relaxed structure, revealing that myosin is switched off by intramolecular interactions between its two heads, the free head and the blocked head. Three-dimensional reconstruction of frozen-hydrated specimens revealed that this asymmetric head interaction is also present in native thick filaments of tarantula striated muscle. Our goal in this study was to elucidate the structural features of the tarantula filament involved in phosphorylation-based regulation. A new reconstruction revealed intra- and intermolecular myosin interactions in addition to those seen previously. To help interpret the interactions, we sequenced the tarantula RLC and fitted an atomic model of the myosin head that included the predicted RLC atomic structure and an S2 (subfragment 2) crystal structure to the reconstruction. The fitting suggests one intramolecular interaction, between the cardiomyopathy loop of the free head and its own S2, and two intermolecular interactions, between the cardiac loop of the free head and the essential light chain of the blocked head and between the Leu305-Gln327 interaction loop of the free head and the N-terminal fragment of the RLC of the blocked head. These interactions, added to those previously described, would help switch off the thick filament. Molecular dynamics simulations suggest how phosphorylation could increase the helical content of the RLC N-terminus, weakening these interactions, thus releasing both heads and activating the thick filament.
PDB ID: 3DTPDownload
MMDB ID: 67196
PDB Deposition Date: 2008/7/15
Updated in MMDB: 2016/12
Experimental Method:
electron microscopy
Resolution: 20  Å
Source Organism:
Avicularia avicularia
Similar Structures:
Biological Unit for 3DTP: 216-meric
Molecular Components in 3DTP
Label Count Molecule
Proteins (216 molecules)
36
Myosin 2 Heavy Chain Chimera of Smooth and Cardiac Muscle
Molecule annotation
36
Myosin 2 Heavy Chain Chimera of Smooth and Cardiac Muscle
Molecule annotation
72
Smooth Muscle Myosin Essential Light Chain
Molecule annotation
72
Myosin Regulatory Light Chain
Molecule annotation
* Click molecule labels to explore molecular sequence information.

Citing MMDB
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