Impact of Regulatory Light Chain Phosphorylation on the Stiffness of α and β Myosin

It has been demonstrated that the phosphorylation of the RLC can also aid in the attachment of myosin heads to actin. Moreover, it has been demonstrated that phosphorylation of the RLC is altered during heart failure progression. Here we examined the role of the RLC, and its phosphorylation, on the motility of α and β Myosin. We characterized the strain dependent kinetics of both myosins by analyzing the dependence of velocity on load using increasing amounts of α-actinin up to 10 μg/ml. As expected, α-myosin, both phosphorylated and dephosphorylated, had a faster actin sliding velocity than β-myosin over the majority of α-actinin concentrations, while phosphorylation of the β-myosin had no significant impact on the actin sliding velocity. Interestingly, although phosphorylation of α-myosin significantly reduced the unloaded sliding velocity it, increased velocity under loaded conditions (See Figure). These results suggest that the phosphorylation of the RLC acts at the molecular level to stiffen the lever arm of myosin aiding in both myosin head attachment and power stroke.View Large Image | View Hi-Res Image | Download PowerPoint Slide