Characterization of P-type ATPase 3 in Plasmodium falciparum

We report the nucleotide sequence, derived amino acid sequence and expressi on profile of P-type ATPase 3 (PfATPase3) from Plasmodium falciparum. An op en reading frame of 7362 nucleotides, interrupted by a single intron of 168 nt, encoded a protein product of 2394 amino acids with a predicted MW of 2 82 791 Da. Hydropathy analysis of PfATPase3 revealed six amino-terminal and six carboxyl-terminal membrane spanning regions (M1-12) flanking a large h ydrophilic domain with a smaller hydrophilic. loop between M4 and M5. Based on a phylogenetic comparison of conserved domains present in P-type ATPase s from other organisms, PfATPase3 resembled a Type-V ATPase for which the t ransport affinity is unknown. The PfATPase3 topology was interrupted by fou r regions, termed 'inserts', unique to malarial P-type ATPases, which were high in asparagine residues and charged amino acids (inserts I1-I4). Insert s I1 and I3 also contained repeated amino acid motifs. The number and compo sition of repeated amino acid motifs in insert I3 were variable in seven P. falciparum strains tested. PfATPase3 was 80.2% similar to the non-insert p ortions of P. yoelii ATPase3, although their inserts differed in length and composition. PfATPase3 mRNA was most abundant relative to beta -tubulin du ring the latter half of the erythrocytic cycle and was also present in game tocytes. Using affinity-purified antibody to a 14 amino acid PfATPase3 epit ope, a 260 kDa protein was detected by Western analysis. Based on immunoflu orescence, the PfATPase3 protein was located intracellularly in gametocytes and, to a lesser extent, in late erythrocytic stages. (C) 2001 Published b y Elsevier Science B.V.