The phorbol ester binding domain consists of a cysteine-rich region with a postulated consensus sequence for binding that includes 15 amino acids (Ahmed, S., Kozma, R., Lee, J., Monfries, C., Harden, N., and Lim, L. (1991) Biochem. J. 280, 233-241). In PKC ζ, the only PKC isoform lacking phorbol ester binding, this region differs in a single residue from the consensus (proline in position 11 of the motif). Restoration of this proline by site- directed mutagenesis of PKC ζ does not restore binding of either [3H]phorbol 12,13-dibutyrate or of the ultrapotent ligand [3H]bryostatin 1, suggesting that even a low affinity ligand interaction is absent. In addition, the vav and c-raf proto-oncogene products, proteins that possess cysteine-rich regions with high homology to PKC isozymes and other phorbol ester receptors, are unable to bind any of these ligands. Instead, all of these cysteine-rich regions bind zinc. Our results suggest that other amino acids besides those postulated for the consensus must be necessary for ligand binding and argue against direct modulation of PKC ζ, Vav, and c-Raf by phorbol esters.
|Original language||English (US)|
|Number of pages||5|
|Journal||Journal of Biological Chemistry|
|State||Published - Apr 15 1994|
ASJC Scopus subject areas
- Molecular Biology
- Cell Biology