Sequential phosphorylation and dephosphorylation of cardiac troponin I by PKA and PP2A generates four different species depending on the active kinase/phosphatase concentration ratio.
This study identifies a new principle of pattern generation in signal cascades involving multiple phosphorylation sites on cardiac troponin I.
Two serine residues located adjacently in the heart-specific N-terminus of cardiac troponin I can be phosphorylated in vivo. Both residues are sequentially phosphorylated and dephosphorylated by cAMP-dependent protein kinase (PKA) and protein phosphatase 2A (PP2A). The concentration changes of the different troponin I species have been determined separately for the phosphorylation and dephosphorylation reaction and approximated by time courses predicted by a reaction model. Dependent on the concentration ratio of active protein kinase/protein phosphatase, four different troponin I species can be generated; one nonphosphorylated, two monophosphorylated and one bisphosphorylated. This pattern generation will be observed in proteins phosphorylated and dephosphorylated by a single protein kinase and phosphatase on more than one site and is a new principle inherent in signal cascades.
Jaquet et al. (Sat,) conducted a other in Cardiac troponin I phosphorylation. cAMP-dependent protein kinase (PKA) and protein phosphatase 2A (PP2A) was evaluated on Concentration changes of different troponin I species. Sequential phosphorylation and dephosphorylation of cardiac troponin I by PKA and PP2A generates four different species depending on the active kinase/phosphatase concentration ratio.