Selective enhanced phosphorylation of shrimp β‐tubulin by PKC‐δ with PEPtaxol, a synthetic peptide encoding the taxol binding region

β-tubulin cDNA from the shrimp Penaeus japonicus was isolated by homology cloning. Expression of cDNA in Escherichia coli yielded a 55 kDa polypeptide, positive for monoclonal antibodies against mammalian β-tubulin. Autoradiography demonstrated the bacterially expressed hepatopancreas β-tubulin of P. japonicus is specifically phosphorylated by the δ isoenzyme of protein kinase C (PKC-δ) purified from the plasma membrane of the shrimp heart, in the presence of the receptor for activated PKC (RACK), but not in its absence. Purified shrimp heart PKC-δ is able to phosphorylate bacterially expressed shrimp β-tubulin without the presence of Ca++, but requires Mg++. The kinase activity of purified PKC-δ on bacterially expressed β-tubulin was enhanced by incubation with PEPtaxol, a synthetic peptide encoding the taxol-binding region of β-tubulin. In other words, PEPtaxol modulates the kinase activity of PKC-δ through RACK. J. Exp. Zool. 292:376–383, 2002. © 2002 Wiley-Liss, Inc.