Both early gametocytes (I-II) and asexual trophozoite stages of Plasmodium
falciparum digest hemoglobin and detoxify haem by polymerizing it into para
site pigment called hemozoin. The mechanism of polymerization is unclear bu
t it has been proposed that histidine-rich protein II may facilitate transp
ort of hemoglobin to the food vacuole and catalyze the polymerization in as
exual stages. We describe the transcription of histidine-rich protein II in
gametocytes by Northern blot analysis and the expression of the protein in
these stages by immunoprecipitation and Western blotting. Localization of
histidine-rich protein II within the gametocyte by immunofluorescence assay
and immunoelectron microscopy clearly illustrated the presence of this mol
ecule in the infected red cell cytosol in the early stages of gametocyte de
velopment and internalization in the later gametocyte as it matures. There
is a strong correlation between the stage-specific trafficking of histidine
-rich protein II in gametocytes and the susceptibility of early but not lat
e gametocytes to the antimalarial drug chloroquine. (C) 2000 Academic Press
.