Expression and characterisation of a Plasmodium falciparum protein containing domains homologous to sarcalumenin and a tyrosine kinase substrate, eps15

We have identified in Plasmodium falciparum a novel gene encoding a putativ e bi-functional protein, termed PfPast-1, from genomic and cDNA libraries. Analysis indicated that the sequence encodes a 62 kDa protein of 529 amino acid residues with two distinctive domains: a sarcalumenin-like domain of a pproximately 320 amino acids at the amino half of the molecule, which share s homology to a major sarcoplasmic reticulum lumenal protein, sarcalumenin, and an eps15 homology domain of about 90 amino acids located at the carbon yl terminus. The eps15 homology domain, first identified in a tyrosine kina se substrate, eps15, and found in increasing numbers of mammalian proteins, has recently been suggested as a protein-protein interaction domain involv ed in intracellular sorting. Genomic sequences encoding similar proteins co ntaining both the sarcalumenin-like and eps15 homology domains have been id entified in humans and Drosophila. RNA blot analysis revealed the presence of a single messenger RNA transcript approximately 3.7 kb in size, which is expressed in all the developmental stages examined with the highest level in extracellular gametes followed by erythrocytic asexual stages, and the l owest in the gametocytes. In the attempt to define its biological function, we have expressed a full-length recombinant PfPast-1 protein in Escherichi a coli. Specific immune serum directed against the recombinant protein reco gnised a similar to 55 kDa protein in the parasite lysate. Further characte risation of PfPast-1 may help in elucidation of its functions in P. falcipa rum. (C) 1999 Australian Society for Parasitology. Published by Elsevier Sc ience Ltd. All rights reserved.