The myosin II coiled-coil domain atomic structure in its native environment

Area of Science:

• Muscle biology
• Structural biology
• Biophysics

Background:

• Thick filaments are essential for muscle contraction, composed primarily of myosin.
• Understanding myosin tail structure is key to elucidating muscle mechanics.

Purpose of the Study:

• To describe the atomic structure of the complete myosin tail in Lethocerus indicus flight muscle.
• To compare this structure with existing crystal structures of human cardiac myosin tail segments.

Main Methods:

• Analysis of thick filaments isolated from Lethocerus indicus flight muscle.
• Comparison with crystal structures of recombinant human cardiac myosin tail segments.

Main Results:

• Good overall agreement between filament and crystal structures, with notable exceptions in proximal S2 and skip regions 2 and 4.
• Detailed atomic description of asymmetric coiled-coil uncoiling at the myosin head-tail junction.
• Unusual structural accommodations in skip regions 2 and 4, including altered helix radius and unfolding.

Conclusions:

• The atomic model provides insights into myosin tail structure within thick filaments.
• Findings may contribute to understanding thick filament mechanosensing and muscle contraction.
• Highlights structural variations influencing myosin tail assembly and function.