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A cardiolipin-activated protein kinase from rat liver structurally distinct from the protein kinases C.

Authors: Morrice, NA  Gabrielli, B  Kemp, BE  Wettenhall, RE 
Citation: Morrice NA, etal., J Biol Chem 1994 Aug 5;269(31):20040-6.
Pubmed: (View Article at PubMed) PMID:8051089

A cardiolipin- and protease-activated protein kinase (PAK) has been isolated from cytoplasmic extracts of rat liver. The enzyme (PAK-1) phosphorylates the ribosomal protein S6-(229-239) peptide analogue and can be activated by limited proteolysis. Partial amino acid sequences of tryptic peptides derived from both the purified 116-kDa PAK-1 holoenzyme and its active catalytic fragment reveal that the catalytic domain is most related (50-58% identity) to the protein kinase C family. PAK-1 has protein and peptide substrate specificities distinct from those of known protein kinase C isoforms and is insensitive to inhibition by the protein kinase C-alpha-(19-31) pseudosubstrate peptide. Phosphatidylserine, diacylglycerol, and phorbol ester do not activate PAK-1 toward the S6 peptide substrate. However, other acidic phospholipids, the most effective being cardiolipin, activate PAK-1 to a similar extent as trypsin. The PAK-1 catalytic activities generated through activation by cardiolipin or limited proteolysis were kinetically similar, with Km values of 3.6 and 3.4 microM, respectively, for the S6-(229-239) peptide substrate. However, differences were observed in the catalytic activities with protamine sulfate and the glycogen synthase-(1-12) peptide analogue as substrates. It was concluded that PAK-1 is a phospholipid-regulated protein kinase with a primary structure, substrate specificity, and mechanism of regulation in vitro distinct from those of any known member of the protein kinase C superfamily.

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CRRD Object Information
CRRD ID: 633689
Created: 2003-08-29
Species: All species
Last Modified: 2004-05-25
Status: ACTIVE



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