A Plasmodium falciparum novel gene encoding a coronin-like protein which associates with actin filaments

Plasmodium falciparum, the major causative agent of human malaria, is an Ap icomplexa protozoan parasite which invades in its intermediate host hepatoc ytes and erythrocytes. The driving force underlying internalization into th e host cell is thought to involve both polymerization of parasite actin, as entry is inhibited by the cytochalasins, and an actin motor-associated pro tein. In the related Apicomplexa parasite, Toxoplasma gondii, the involveme nt of parasite actin during both processes of motility and host cell entry has been genetically established. In a search for molecules that can regula te actin dynamics within Apicomplexa parasites, we have identified a P. fal ciparum homologue of the actin associated protein called coronin originally described in the amoeba Dictyostelium discoideum. The single copy gene dis plays a strong homology with the amoeba sequence and with the bovine and hu man coronin homologues recently cloned. This homology lies not only within the N-terminus containing the five WD repeats that characterize coronin but also extends in the C-terminal part. Furthermore, using an affinity-purifi ed mouse monoclonal antibody against D. discoideum coronin, we have detecte d in extracts of P. falciparum young and mature schizonts a 42-kDa polypept ide which binds this antibody and is present in a Triton insoluble fraction that also contains parasite actin filaments. In addition, the recombinant protein encoded by the homologue nucleotidic sequence of P. falciparum coro nin is indeed recognized by the antibody against D. discoideum coronin. Fin ally, the cross-reactive polypeptide displays the ability to cosediment wit h exogenous F-actin, a property which fits with its involvement in actin dy namics. (C) 1998 Federation of European Biochemical Societies.