Does a histidine-rich protein from Plasmodium lophurae have a function in merozoite penetration?

Autoradiography was used to localize the distribution of L-[3H]histidine incorporated in vitro by developing segmenters of Plasmodium lophurae. Under conditions used for the visualization of high specific activity loci, radioactivity appeared associated mainly with the histidine-rich protein of cytoplasmic granules as well as with rhoptries and micronemes of merozoites. The isolated histidine-rich protein caused agglutination of erythrocytes and increased their osmotic fragility. Based on the observed evidence suggesting the presence of this histidine-rich protein in the polar organelles of merozoites and its reactivity with erythrocyte membranes, the hypothesis that such a protein may have a function in the penetration of merozoites is proposed.