STAGE-SPECIFIC SUBSTRATE PHOSPHORYLATION BY A CA2+ CALMODULIN-DEPENDENT PROTEIN-KINASE IN TRYPANOSOMA-CRUZI/

The presence of Ca2+/calmodulin (Ca2+/CaM)-dependent protein kinase (T cCaM K) and some stage-specific substrates that appeared during morpho genesis of the parasite Trypanosoma cruzi were identified. Western blo t analysis using a polyclonal antibody against rat brain CaM K type II recognized the same subunit composition (52, 59/62 kDa) observed for the mammalian enzyme, as well as the previously characterized TcCaM K found in epimastigote forms. Differential protein phosphorylation prof iles were observed after enzyme activation in the stages of T. cruzi. Co-immunoprecipitation of stage-specific substrates with the TcCaM K s uggested that the enzyme might be involved in the phosphorylation of a different set of proteins through the life cycle. Three phosphoprotei ns, pp105 and pp87 from epimastigotes and pp23 from trypomastigotes we re identified as potential substrates for TcCaM K. The characterizatio n of these endogenous stage markers might be a useful tool to understa nd the developmental cycles of these pathogenic protozoa.