Molecular analysis of a P-type ATPase from Cryptosporidium parvum.

Eukaryotic P-type ATPases use energy to drive the transport of cations across membranes. A complete P-ATPase gene (CpATPase1) has been isolated from Cryptosporidium parvum, one of the opportunistic pathogens in AIDS patients. The complete gene encodes 1528 amino acids, predicting a protein of 169 kDa. A hydropathy profile of the protein suggested there are eight transmembrane domains (TM). Expression of the gene was confirmed both by Northern blot analysis and RT-PCR. A fragment of the gene has been expressed as a 49 kDa GST-fusion protein. This protein was used to produce rabbit antiserum and fluorescent labeling has localized the protein to the sporozoite apical and perinuclear regions. SDS-PAGE and Western blot analysis show a 160 kDa major protein, close to the predicted size. The protein shares greatest overall identity and similarity to a putative organellar Ca2+ P-ATPase described for Plasmodium falciparum. Unlike P. falciparum, but consistent with all genes so far isolated from C. parvum, the gene contains no introns. The Ca2+ P-ATPases from these two Apicomplexa are large and do not have motifs predicting calmodulin-binding.