Key result
NM2-B filaments move processively along actin while NM2-A requires higher viscosity or NM2-B copolymerization.
This in vitro study demonstrates that the kinetic and mechanical properties of nonmuscle myosin 2 filaments can be tuned by their subunit composition and environmental viscosity, suggesting a cellular strategy for tailoring force production.
Nonmuscle myosin 2 (NM-2) powers cell motility and tissue morphogenesis by assembling into bipolar filaments that interact with actin. Although the enzymatic properties of purified NM-2 motor fragments have been determined, the emergent properties of filament ensembles are unknown. Using single myosin filament in vitro motility assays, we report fundamental differences in filaments formed of different NM-2 motors. Filaments consisting of NM2-B moved processively along actin, while under identical conditions, NM2-A filaments did not. By more closely mimicking the physiological milieu, either by increasing solution viscosity or by copolymerization with NM2-B, NM2-A containing filaments moved processively. Our data demonstrate that both the kinetic and mechanical properties of these two myosins, in addition to the stochiometry of NM-2 subunits, can tune filament mechanical output. We propose altering NM-2 filament composition is a general cellular strategy for tailoring force production of filaments to specific functions such as maintaining tension or remodeling actin.
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Melli et al. (2017) studied this question. Nonmuscle myosin 2-A and 2-B filaments was evaluated on Filament processivity and velocity. Filaments consisting of NM2-B moved processively along actin, whereas NM2-A filaments required increased solution viscosity or co-polymerization with NM2-B to move processively.
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