In the October 3 Nature, Laurence Florens and colleagues describe a large-scale proteomic study that complements the genome sequencing approach to understanding the malaria parasite Plasmodium falciparum (Nature, 419:520-526, October 3, 2002).
The Plasmodium life cycle is extremely complex, as the parasite must adapt to both vertebrate and invertebrate hosts, invade different cell types and evade the immune system. As a consequence of this, not all the stages of the parasite life cycle are amenable to cultivation and characterization in vitro.
Florens et al. analyzed the proteome isolated from different stages; sporozoites (the human infectious form), merozoites (the invasive stage), trophozoites (the form multiplying in erythrocytes) and gametocytes (sexual stages). Using multidimensional protein identification technology (MudPIT) they were able to detect about half of the predicted Plasmodium genes in the four stages - only 6% of proteins were common to all four stages.
The sporozoite proteome was very different from the others with half of the proteins unique to this stage. The merozoite stage was characterized by the expression of surface proteins that mediate invasion and immune evasion. Serine proteases - important for the digestion of hemoglobin - are expressed at the trophozoite stage and gametocyte-specific proteins, ribonucleoproteins and transcription factors were identified in the gametocyte proteome.
When they mapped the expressed genes back on to the Plasmodium genome they found that co-expressed proteins were often located in chromosomal clusters suggesting coordinated regulatory mechanisms.
Florens L Washburn MP, Raine DJ, Anthony RM, Grainger M, Haynes JD, J. Moch K, Muster N, Sacci JB, Tabb DL, et al.: A proteomic view of the Plasmodium falciparum life cycle Nature, 419:520-526, October 3, 2002.
Sanger Institute Protozoan Genomes - Plasmodium falciparum
Spellman PT, Rubin JM: Evidence for large domains of similarly expressed genes in the Drosophila genome Journal of Biology, 1:5, June 18, 2002.