A Plasmodium falciparum aminopeptidase gene belonging to the M1 family of zinc-metallopeptidases is expressed in erythrocytic stages

A new single copy gene has been isolated from Plasmodium falciparum, by imm unoscreening a genomic DNA expression library. The gene appears devoid of i ntrons, displays the classical A + T richness and codon usage of P. falcipa rum genes, and is transcribed into a 4 kb mRNA in erythrocytic stages. The deduced amino acid sequence corresponds to a 1056 residue protein (122 kDa) containing the canonical HExxHx(18)E signature of zinc-metallopeptidase ac tive sites of the M1 family at position 467-490, a downstream conserved tyr osine residue involved in catalysis in position 551, and the GAMEN conserve d motif characteristic of aminopeptidases in the M1 family, at position 431 -435. The greatest similarities were found with aminopeptidases N of Escher ichia coli and Haemophilius influenza (more than 80% identical residues in the canonical signature of the active site) but significant similarities ce ntred on the active site region exist with all other members of the M1 fami ly such as other prokaryotic aminopeptidases, eukaryotic aminopeptidases A and N and leukotriene A4 hydrolases (40-50% identical residues in the canon ical signature of the active site). A polyclonal serum raised to a syntheti c peptide deduced from the gene labelled schizont proteins of 96 and 68 kDa purified to homogeneity and both displaying aminopeptidase activity, as we ll as cytoplasmic structures in schizont stages. (C) 1998 Published by Else vier Science B.V. All rights reserved.