Key Points
- To investigate in vitro phosphorylation of myofibrillar proteins across cardiac and skeletal muscles by the catalytic subunit of cAMP-dependent protein kinase to understand catecholamine-mediated contractile regulation.
- Incubated canine red skeletal, rabbit white skeletal, and bovine cardiac myofibrils and isolated proteins with the isolated catalytic subunit of cAMP-dependent protein kinase and Mg-[γ-32P]ATP.
- Quantified phosphate incorporation into C-proteins and evaluated their functional effects on actomyosin Mg2+-ATPase activity in reconstituted skeletal and desensitized cardiac actomyosin systems.
- Bovine cardiac C-protein was phosphorylated to 5–6 mol Pi/mol C-protein, whereas canine red and rabbit white skeletal muscle C-proteins incorporated ~0.5 mol Pi/mol C-protein.
- Phosphorylation of cardiac C-protein enhanced its inhibitory effect on desensitized cardiac actomyosin Mg2+-ATPase activity, while phosphorylation of skeletal or cardiac C-protein had no effect on reconstituted skeletal actomyosin ATPase inhibition.
Structured PICO
PPopulationIn vitro models using canine red skeletal myofibrils, rabbit white skeletal muscle, and bovine cardiac muscle
IInterventionIncubation with the isolated catalytic subunit of cAMP-dependent protein kinase and Mg-[γ-32P]ATP
OOutcomePhosphorylation of C-proteins and effect on actin-activated myosin Mg2+-ATPase activitysurrogate
Phosphorylation of cardiac C-protein by cAMP-dependent protein kinase enhances its inhibitory effect on actomyosin Mg2+-ATPase, providing insight into the biochemical basis of catecholamine effects on cardiac contractility.