CHARACTERIZATION OF A PLASMODIUM-VIVAX CYSTEINE PROTEINASE GENE IDENTIFIES UNIQUELY CONSERVED AMINO-ACIDS THAT MAY MEDIATE THE SUBSTRATE-SPECIFICITY OF MALARIAL HEMOGLOBINASES

The gene encoding a cysteine proteinase of the human malaria parasite Plasmodium vivax has been identified and characterized. The sequence predicted by the proteinase gene shares several unique features with the sequences of two recently characterized cysteine proteinases of other malarial species. These features include the conservation of a number of amino acids that are predicted, based on a recently devised model for the related Plasmodium falciparum cysteine proteinase, to be located near the enzyme's active site. We hypothesize that these residues have been conserved to maintain optimal proteolytic specificity in the hydrolysis of globin by malaria parasites.