The composition of haemozoin from Plasmodium falciparum.

Haemozoin (malaria pigment) was isolated from 2 strains of Plasmodium falciparum cultivated in vitro. The purest preparations contained 41 to 45% ferriprotoporphyrin IX and a glycine-rich polypeptide ('apohaemozoin') of approximately 14 kDa molecular weight which is synthesized by the parasite. In the two strains studied, NF54 and K1, it was calculated that about 15 and 18 iron porphyrin molecules, respectively, were associated with each molecule of apohaemozoin, which contained more hydrophobic amino acid residues in strain K1. One molecule of iron porphyrin was associated with every 9-10 amino acid residues in the haemozoin of both strains. Our observations support the idea that the intraerythrocytic malaria parasite, incapable of cleaving the haem ring, detoxifies the iron porphyrin residuum from haemoglobin digestion in a crystalline complex with a specially synthesized protein.