Multiple-antigenic peptides of histidine-rich protein II of Plasmodium falciparum:: Dendrimeric biomineralization templates

A critical target for the development of new antimalarial treatments is the detoxification pathway of free heme released during the catabolism of host hemoglobin in the digestive vacuole of the malaria parasite Plasmodium falciparum, We have examined a family of peptide dendrimers (BNT I and II) based on the tandem repeat motif of HRP II from P. falciparum for their abilities both to bind heme substrates and to form the critical detoxification polymer hemozoin. Each template was capable of binding significant amounts of the natural substrate, Fe(III)PPIX. Binding of the metal-free base protoporphyrin IX to the templates suggests, however, that substrate recognition is based on the porphyrin moiety rather than specific metal recognition. Such a supposition is further supported by the fact that Zn(II)PPIX, as well as the structurally related metal-free and metallophthalocyanines, can bind to the templates. Further, it was shown that the dendrimeric BNT I and BNT II were capable of supporting the polymerization of hemozoin. In light of previously reported binding studies of linear sequences derived from HRP II and the polymer polyhistidine, the results suggest that the tandem organization of the tripeptide binding sites promotes the formation of hemozoin for these model templates.