Exogenous substrate stimulates autodephosphorylation of cyclic-AMP-dependent protein kinase II.
The autophosphorylated regulatory subunit (32P-RII) of cyclic-AMP-dependent protein kinase II was efficiently dephosphorylated by its C subunit in the absence of added ADP, provided that Mg/ATP and a standard protein kinase peptide substrate were present. This raises the possibility that autodephosphorylation could be significant in the intact cell. Only the cyclic-AMP-complexed free form of 32P-RII was efficiently dephosphorylated, indicating that the autodephosphorylation was intermolecular. Autodephosphorylation of 32P-RII in the presence of MgATP and kemptide occurred with formation of [gamma-32P]ATP, suggesting transfer of 32P of phospho-RII to a transient C*(MgADP) complex formed during the forward kinase reaction with peptide as substrate. Autodephosphorylation promoted by phosphorylation of exogenous substrates could operate also for other kinases conforming to a mechanism where MgADP remains bound to the active site after the other product (phosphorylated substrate) has left the catalytic complex.
Department of Anatomy and Cell Biology, University of Bergen, Norway.
B T
BT
Gjertsen
B
B
Fauske
S O
SO
Døskeland
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000494:pharmacology; D000595:Amino Acid Sequence; D000818:Animals; D002417:Cattle; D000242:Cyclic AMP / Q000378:metabolism / Q000494:pharmacology*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000378:metabolism / Q000494:pharmacology; D010749:Phosphoprotein Phosphatases / Q000037:antagonists & inhibitors / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D011494:Protein Kinases / Q000378:metabolism*
D009842:Oligopeptides; D010750:Phosphoproteins; D000244:Adenosine Diphosphate; C037642:kemptide; D000255:Adenosine Triphosphate; D000242:Cyclic AMP; D011494:Protein Kinases; D010749:Phosphoprotein Phosphatases