MOLECULAR-CLONING AND CHARACTERIZATION OF A NOVEL ACIDIC MICRONEME PROTEIN (ETMIC-2) FROM THE APICOMPLEXAN PROTOZOAN PARASITE, EIMERIA-TENELLA

A 50 kDa acidic protein, which is found within the microneme organelle s of Eimeria tenella sporozoites and merozoites and called E. tenella mic-2, was cloned by immunoscreening of a cDNA expression library. The expression of the protein and its mRNA during the developmental cycle of the parasite was consistent with de novo formation of microneme or ganelles during both sporulation and schizogony. Although micronemal i n origin, indirect immunofluorescent antibody labelling on gluraraldeh yde fixed parasites, indicated that the protein was translocated to th e sporozoite surface, and, during host cell invasion the protein was f ocussed at the point of parasite entry and secreted from the host-para site interface. Either during or just after invasion, Etmic-2 protein became transiently dispersed over the entire surface of the infected c ell. One hour after adding sporozoites to host cells, no delectable Et mic-2 protein remained on the host cell surface. A full length cDNA co rresponding to Etmic-2 predicted a protein with a classical signal pep tide that preceded the mature N-terminus of the protein as determined by direct microsequencing. Regions of the Etmic-2 protein have highly significant similarities to regions within Drosophila melanogaster tro pomyosin II and within two known substrates of the cellular regulatory enzyme protein kinase C.