Key Points
- The study aims to explore how calmodulin binding influences the phosphorylation of smooth muscle myosin kinase by cAMP-dependent protein kinase.
- Investigated calmodulin binding to smooth muscle myosin light chain kinase in calcium presence.
- Analyzed the effects of phosphorylation and dephosphorylation on the activity of myosin kinase using purified phosphatase.
- Confirmed the existence of phosphorylation sites by tryptic digestion of denatured myosin kinase.
- Phosphorylation significantly decreased myosin kinase activity by requiring 10-20 times more calmodulin for 50% activation.
- When calmodulin is bound, phosphorylation occurs at one site with no impact on enzyme activity.
- Two phosphorlyation sites in myosin kinase were identified.
Structured PICO
PPopulationSmooth muscle myosin light chain kinase
IInterventionPhosphorylation by cAMP-dependent protein kinase in the presence or absence of calmodulin
CComparatorUnphosphorylated state or presence vs absence of calmodulin
OOutcomeMyosin kinase activity and number of phosphorylation sitessurrogate
Phosphorylation of smooth muscle myosin light chain kinase by cAMP-dependent protein kinase decreases its activity only when calmodulin is not bound, by increasing the amount of calmodulin required for activation.