Protein kinase C contains two phorbol ester binding domains.
A series of deletion and truncation mutants of protein kinase C (PKC) were expressed in the baculovirus-insect cell expression system in order to elucidate the ability of various domains of the enzyme to bind phorbol dibutyrate (PDBu). A PKC truncation mutant consisting of only the catalytic domain of the enzyme did not bind [3H]PDBu, whereas a PKC truncation mutant consisting of the regulatory domain (containing the tandem cysteine-rich putative zinc finger regions) bound [3H]PDBu. Deletion of the second conserved region (C2) of PKC did not abolish [3H]PDBu binding, whereas a deletion of the first conserved region (C1) of PKC, containing the two cysteine-rich sequences, completely abolished [3H]PDBu binding. Additional truncation and deletion mutants helped to localize the region necessary for [3H]PDBu binding; all PKC mutants that contained either one of the cysteine-rich zinc finger-like regions possessed phorbol ester binding activity. Scatchard analyses of these mutants indicated that each bound [3H]PDBu with equivalent affinity (21-41 nM); approximately 10-20-fold less than the native enzyme. In addition, a peptide of 146 amino acid residues from the first cysteine-rich region, as well as a peptide of only 86 amino acids residues from the second cysteine-rich region, both bound [3H]PDBu with high affinity (31 +/- 4 and 59 +/- 13 nM, respectively). These data establish that PKC contains two phorbol ester binding domains which may function in its regulation.
Department of Biochemistry, Duke University Medical Center, Durham, North Carolina 27710.
D J
DJ
Burns
R M
RM
Bell
D000595:Amino Acid Sequence; D016367:Baculoviridae / Q000235:genetics; D001483:Base Sequence; D015153:Blotting, Western; D002384:Catalysis; D004247:DNA / Q000235:genetics; D004591:Electrophoresis, Polyacrylamide Gel; D005814:Genes, Viral; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation; D015240:Phorbol 12,13-Dibutyrate / Q000378:metabolism*; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
D007527:Isoenzymes; D015240:Phorbol 12,13-Dibutyrate; D004247:DNA; D011493:Protein Kinase C