Substrate specificity of rat brain calcium-activated and phospholipid-dependent protein kinase.
A synthetic peptide ArgThrProProProSerGly with sequence similar to the threonine sites of phosphorylation in both myelin basic protein and simian virus 40 T antigen could be phosphorylated in vitro by a purified rat brain Ca2+-activated and phospholipid-dependent protein kinase, protein kinase C. The apparent Km and Vm values of this heptapeptide for the enzyme were determined to be 240 microM and 60 nmol/min/mg, respectively. Up to 0.8 mol 32P could be incorporated into the peptide, mainly at the threonine residue. Substitution of the L-threonine residue in the heptapeptide by its D-enantiomer abolished the phosphorylatability of the peptide by protein kinase C. However, this (D)Thr-containing peptide could act as a competitive inhibitor for the kinase with an apparent Ki value of approximately 320 microM. These findings suggest that a triprolyl sequence may act as a recognition site for protein kinase C.
Chan
K F
KF
Stoner
G L
GL
Hashim
G A
GA
Huang
K P
KP
D000818:Animals; D001667:Binding, Competitive; D001921:Brain / Q000201:enzymology*; D009842:Oligopeptides / Q000378:metabolism; D010718:Phosphatidylserines / Q000502:physiology; D010766:Phosphorylation; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D051381:Rats; D013329:Structure-Activity Relationship; D013379:Substrate Specificity; D013912:Threonine / Q000378:metabolism
D009842:Oligopeptides; D010718:Phosphatidylserines; C047909:arginyl-threonyl-prolyl-prolyl-prolyl-seryl-glycine; D013912:Threonine; D011493:Protein Kinase C