Key Points
- Determine whether phosphorylation of the 20,000-dalton light chain by endogenous myosin light chain kinase regulates the actin-activated ATPase activity of macrophage myosin.
- Purified myosin in an unactivated state from rabbit alveolar macrophages.
- Phosphorylated the isolated myosin using endogenous myosin light chain kinase to evaluate phosphate incorporation onto the 20,000-dalton light chain.
- Measured actin-activated MgATPase enzymatic activity across varying levels of light chain phosphorylation at 37 °C.
- Phosphorylation localized specifically to the 20,000-dalton myosin light chain, incorporating up to 2 mol of phosphate per mol of myosin.
- Actin-activated ATPase activity varied directly with the degree of phosphorylation, reaching a maximal MgATPase activity of approximately 200 nmol Pi/mg myosin/min at 37 °C upon full phosphorylation (2 mol Pi/mol myosin).
Structured PICO
PPopulationMyosin purified from rabbit alveolar macrophages
IInterventionPhosphorylation by endogenous myosin light chain kinase
OOutcomeActin-activated ATPase activitysurrogate
Phosphorylation of the 20,000-dalton light chain of myosin is sufficient to regulate the actin-activated ATPase activity of macrophage myosin.