Key result
Replacing the native regulatory light chain MLC2f with MLC2v transformed the fast skeletal muscle myosin II isoform into a processive motor, increasing its association rate toward ATP and actin by >2-fold.
Why the study?
Precise insights into how light chains contribute to functional variabilities among myosin family motors remained unresolved.
Replacing the regulatory light chain in fast skeletal myosin II with a slow muscle variant transforms it into a processive motor, highlighting the role of light chains in fine-tuning mechanical output.
Light chain engineering yields processive myosin; leaves open cardiac therapeutic translation.
Myosin family motors play diverse cellular roles. Precise insights into how the light chains contribute to the functional variabilities among myosin motors, however, remain unresolved. Here, it is demonstrated that the fast skeletal muscle myosin II isoform myosin heavy chain (MHC-IID) can be transformed into a processive motor, by simply replacing the native regulatory light chain MLC2f with the regulatory light chain variant MLC2v from the slow muscle myosin II. Single molecule kinetic analyses and optical trapping measurements of the hybrid motor reveal marked changes such as increased association rate of myosin toward adenosine triphosphate (ATP) and actin by more than twofold. The direct consequence of high adenosine diphosphate (ADP) affinity and increased actin rebinding is the altered overall actomyosin association time during the cross-bridge cycle. The data indicate that the MLC2v influences the duty ratio in the hybrid motor, suggestive of promoting interhead communication and enabling processive movement. This finding establishes that the regulatory light chain fine-tunes the motor's mechanical output that may have important implications under physiological conditions. Furthermore, the success of this approach paves the way to engineer motors from a known motor protein element to assemble highly specialized biohybrid machines for potential applications in nano-biomedicine and engineering.
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Amrute‐Nayak et al. (2019) studied this question. Replacing native regulatory light chain MLC2f with MLC2v vs. Native fast skeletal muscle myosin II isoform (MHC-IID) was evaluated on Association rate toward ATP and actin. Replacing the native regulatory light chain MLC2f with MLC2v transformed the fast skeletal muscle myosin II isoform into a processive motor, increasing its association rate toward ATP and actin by >2-fold.
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