Biochemical and immunological studies of protein kinase C from Trypanosoma cruzi

Phorbol ester binding was studied in protein kinase C-containing extracts obtained from Trypanosoma cruzi epimastigote forms. Specific 12-O-tetradecanoyl phorbol 13-acetate, [3H]PMA, or 12,13-O-dibutyryl phorbol, [3H]PDBu, binding activities, determined in T. cruzi epimastigote membranes, were dependent on ester concentration with a Kd of 9x10(-8) M and 11.3x10(-8) M, respectively. The soluble form of T. cruzi protein kinase C was purified through DEAE-cellulose chromatography. Both protein kinase C and phorbol ester binding activities co-eluted in a single peak. The DEAE-cellulose fraction was further purified into three subtypes by hydroxylapatite chromatography. These kinase activity peaks were dependent on Ca2+ and phospholipids and eluted at 40 mM (PKC I), 90 mM (PKC II) and 150 mM (PKC III) phosphate buffer, respectively. Western blot analysis of the DEAE-cellulose fractions, using antibodies against different isoforms of mammalian protein kinase C enzymes, revealed that the parasite expresses high levels of the alpha-PKC isoform. Immunoaffinity purified T. cruzi protein kinase C, isolated with an anti-protein kinase C antibody-sepharose column, were subjected to phosphorylation in the absence of exogenous phosphate acceptor. A phosphorylated 80 kDa band was observed in the presence of Ca2+, phosphatidylserine and diacylglycerol.