Why the study?
It remains an outstanding question whether myosin heavy chain isoforms alone account for distinct physiological properties or if different regulatory light chains contribute to functional diversification.
Does swapping regulatory light chains alter the mechanical output and sliding speed of skeletal myosin-II isoforms?
Does swapping regulatory light chains alter the mechanical output and sliding speed of skeletal myosin-II isoforms?
Demonstrates that regulatory light chains play a crucial role in fine-tuning the mechanical output and function of skeletal myosin-II isoforms.
Myosin II is the main force generating motor during muscle contraction. Myosin II exists as different isoforms, involved in diverse physiological functions. The outstanding question is whether the myosin heavy chain (MHC) isoforms alone account for the distinct physiological properties. Unique sets of essential and regulatory light chains (RLCs) assembled with specific MHCs raises an interesting possibility of specialization of myosin functions via light chains (LCs). Here, we ask whether different RLCs contribute to the functional diversification. To investigate this, we generated chimeric motors by reconstituting MHC fast isoform (MyHC-IId) and slow isoform (MHC-I) with different light chain variants. As a result of RLCs swapping, actin filament sliding velocity increased by ∼ 10 fold for the slow myosin and decreased by >3 fold for the fast myosin. Ensemble molecule solution kinetics and single molecule optical trapping measurements provided in-depth insights into altered chemo mechanical properties of the myosin motors, thereby affecting the sliding speed. We find that both slow and fast myosins mechanical output is sensitive to the RLC isoform and propose that RLCs are crucial in fine-tuning of the myosin function.
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Nayak et al. (2020) studied this question.
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