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Properties, stage-dependent expression and localization of Plasmodium falciparum M1 family zinc-aminopeptidase

Published online by Cambridge University Press:  16 January 2003

M. ALLARY
Affiliation:
Laboratoire de Biologie Parasitaire, Protistologie, Helminthologie, Muséum National d'Histoire Naturelle, EA 3335 et FR 63 CNRS, 61 rue Buffon, 75231 Paris cedex 05, France
J. SCHREVEL
Affiliation:
Laboratoire de Biologie Parasitaire, Protistologie, Helminthologie, Muséum National d'Histoire Naturelle, EA 3335 et FR 63 CNRS, 61 rue Buffon, 75231 Paris cedex 05, France
I. FLORENT
Affiliation:
Laboratoire de Biologie Parasitaire, Protistologie, Helminthologie, Muséum National d'Histoire Naturelle, EA 3335 et FR 63 CNRS, 61 rue Buffon, 75231 Paris cedex 05, France

Abstract

A Plasmodium falciparum single copy gene predicting a 122 kDa protein belonging to the M1 family of zinc-metallopeptidases was previously reported and related to erythrocytic schizont proteins of 96 (p96) and 68 (p68) kDa. By using protease inhibitors during parasite harvest and enzyme preparations, and polyclonal antibodies specific for 2 peptidic domains deduced from the gene, we identified the 120 kDa precursor and demonstrated its processing into p96 and p68. The N-terminal ends of p96 and p68 were mapped between glycine-123 and lysine-163, both proteins thus containing the catalytic domain. The purified enzyme, here named PfA-M1 (p96/p68), displayed strict aminopeptidase activity, optimal at pH 7·4, with broad substrate spectrum. Its inhibition and reactivation profiles were typical of zinc-metalloaminopeptidases. By Western blotting, PfA-M1 was detected in trophozoites, in addition to schizonts, but not in early rings. PfA-M1 was localized by indirect immunofluorescence confocal microscopy. In trophozoites, the labelling was diffuse in the parasite cytoplasm, with accumulations around the food vacuole. In schizonts, it turned progressively to a vesicle-like pattern, ending as a clear spot in released merozoites. The involvement of PfA-M1 in haemoglobin breakdown and erythrocyte reinvasion is discussed in light of the dual functions recently reported for several P. falciparum proteases.

Type
Research Article
Copyright
2002 Cambridge University Press

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