Plasmodium protein phosphatase 2C dephosphorylates translation elongation factor 1 beta and inhibits its PKC-mediated nucleotide exchange activity invitro

The elongation step of protein synthesis involves binding of aminoacyl-tRNA to the ribosomal A site, formation of a peptide bond and translocation of the newly formed peptidyl-tRNA to the P site. The nucleotide exchange facto r EF-1 beta plays a major role in the regulation of this process by regener ating a GTP-bound EF-1 alpha necessary for each elongation cycle. EF-1 beta has been shown to be phosphorylated and its phosphorylation is critical fo r optimal activity. We have previously identified a serine/threonine protei n phosphatase 2C (PP2C) from the human malaria parasite Plasmodium falcipar um, In the current work, we performed Far-Western analysis to identify PfPP 2C substrates. Several components of the translation and transcription mach inery were identified, including translation elongation factor 1-beta (PfEF -1 beta). PfEF-1 beta is efficiently phosphorylated by protein kinase C and this phosphorylation results in a 400% increase in its nucleotide exchange activity. PKC-phosphorylated PfEF-1 beta is readily and selectively dephos phorylated by recombinant and native PfPP2C, which downregulates the nucleo tide exchange activity to its basal level,The identification of a translati on elongation component as substrate for PP2C suggests an important regulat ory function for this enzyme and suggests that it may be a good target for drug design in the fight against malaria.