Sequence of a cDNA encoding a small polymorphic histidine- and alanine-rich protein from Ptasmodium falciparum

We describe the expression in Escherichia coli, isolation by immunological screening and complete nucleotide sequence of a cDNA clone from the malaria parasite Plasmodium falciparum. The deduced amino acid sequence contains separate blocks of repetitive hexapeptide and pentapeptide sequences and we have confirmed that these represent epitopes by reaction of the corresponding synthetic peptides with human antibodies. As the predicted size is Mr 21,000 and the overall composition is 30% His and 29% Ala, the polypeptide has been termed the small histidine-alanine rich protein (SHARP). This polypeptide is highly polymorphic in different P.falciparum isolates and cross reacts immunologically with a distinct gene product of P.falciparum. Although it is related to the Histidine Rich Protein (HRP) of P.lophurae by virtue of its high His content, it shows no obvious sequence relationship to the HRP outside the repeats.