Light chain-dependent myosin structural dynamics in solution investigated by transient electrical birefringence

Area of Science:

• Biophysics
• Muscle Physiology
• Protein Dynamics

Background:

• Myosin subfragment 1 (S1) is crucial for muscle contraction.
• The roles of essential (elc) and regulatory (rlc) light chains in S1's mechanical properties are not fully understood.
• Understanding S1 dynamics is key to elucidating muscle force generation mechanisms.

Purpose of the Study:

• To compare the electric and structural dynamic properties of S1(elc, rlc) and S1(elc).
• To investigate the influence of regulatory light chains on S1's stiffness and flexibility.
• To explore how these properties relate to muscle force production.

Main Methods:

• Transient electrical birefringence was employed to measure electric and dynamic properties.
• Rotational Brownian motion analysis was used to determine size and flexibility.
• Electric field application was used to assess structural distortion and segmental flexibility.

Main Results:

• S1(elc, rlc) is larger and possesses a greater permanent electric dipole moment than S1(elc).
• Both S1 forms exhibit segmental flexibility, but S1(elc, rlc) is significantly stiffer and resistant to electric field distortion.
• The S1 . MgADP . Vi complex is smaller than S1 . MgADP, with the S1(elc, rlc) . MgADP . Vi complex retaining flexibility.

Conclusions:

• Regulatory light chains increase the size and stiffness of myosin subfragment 1.
• Myosin subfragment 1 exhibits intrinsic segmental flexibility, which is modulated by light chain composition.
• These findings contribute to understanding the molecular mechanisms of muscle contraction and force generation.