Isolation and characterization of a structural homologue of human PRK2 from rat liver. Distinguishing substrate and lipid activator specificities.
A homologue of human protein kinase C (PKC)-related kinase-2, PRK2, which had previously escaped identification in normal mammalian tissues, was isolated from rat liver as the protease-activated kinase ( PAK) originally named PAK-2. The 130-kDa cytosolic enzyme was purified to homogeneity and shown by tryptic peptide and reverse transcriptase- polymerase chain reaction (RT-PCR)-amplified rat cDNA sequence analyses to be structurally related to the 116-kDa rat hepatic PAK-1/ protein kinase N ( PKN) and, even more closely (95% sequence identity) to the 130-kDa human PKC-related kinase, PRK2. Rat myeloma RNA was used as the RT-PCR template because of its relative abundance in PAK-2/PRK2 mRNA compared with liver and other rat tissues. The catalytic properties of PAK-2/PRK2 in many respects resembled those of hepatic PAK-1/ PKN, but were distinguished by more favorable kinetics with several peptide substrates, and greater sensitivity to PKC pseudosubstrate and polybasic amino acid inhibitors. PAK-2/PRK2 was also activated by lipids, particularly cardiolipin and to a lesser extent by other acidic phospholipids and unsaturated fatty acids. Cardiolipin activation was most evident with autophosphorylation and histone H2B phosphorylation, but only marginally evident with the favored ribosomal S6-(229-239) peptide substrate for the protease-activated kinase activity. It was concluded that PAK-2 is the rat homologue of human PRK2, with biochemical properties distinct from although overlapping those of the PAK-1/ PKN/PRK1 isoform.[1]References
- Isolation and characterization of a structural homologue of human PRK2 from rat liver. Distinguishing substrate and lipid activator specificities. Yu, W., Liu, J., Morrice, N.A., Wettenhall, R.E. J. Biol. Chem. (1997) [Pubmed]
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