Structure and possible function of heat-shock proteins in Falciparum malaria.

Like many prokaryotes and eukaryotes, the malaria parasite also synthesizes several stress proteins. Most widely studied stress proteins of this parasite are the heat-shock proteins (hsps). Their discovery in malaria is a gift of recombinant DNA technology. Five hsp genes from Plasmodium falciparum have been identified which are located on different chromosomes. Thus the inheritance and expression of hsp genes are independent of each other. They share a large amount of sequence homology at N-terminus with the hsps of other organisms. Their gene regulatory sequences and other elements, important for gene expression, are yet to be determined. The biological role of these proteins in malaria is not fully understood but it is possible that they provide protection to the parasite from various stresses encountered in the host. In this process hsps probably bind to the toxic molecules as well as damaged proteins to flush them out of the parasite. Their involvement in the stage-specific parasite transformation to increase the infectivity and virulence, as observed in other parasites, remains to be determined. Malarial hsps are antigenic in humans. This antigenicity could be attributed to the non-homologous sequences in the C-terminus region. The potential of one of them (pfhsp 70I) for a future malaria vaccine and immunodiagnostics requires re-evaluation of the data.