Discussion

The malaria parasite’s cycle of replication and proliferation in the asexual blood stage of the life cycle alternates between intracellular and extracellular phases, with the extracellular merozoite being very short lived. Each cycle, the parasite has to elaborate and assemble a new food vacuole and all the subcellular structures necessary for merozoite invasion of an erythrocyte as well as discarding or disassembling them once their function has been fulfilled. Whilst we know quite a bit about the importance of gene expression in these processes, the role of protein modification and degradation is less well understood. The transition from schizont to merozoite is accompanied by extensive protein phosphorylation and ubiquitylation. We suggest that phosphorylation provides a rapid and dynamic way to control protein function and that ubiquitylation prepares merozoite proteins for rapid degradation once their function is completed, enabling reuse of scarce resources in the early intracellular parasite.