Objective: p195, the major protein on the surface of Plasmodium falciparum merozoites, has been found to have ability to bind sialic acid residues on the surface of human erythrocytes, and this binding is thought to be a prerequisite for recognition of human erythrocyte by merozoite- This study attempted to map out the binding site of p195, thus providing a theoretical clue to developing an antimalaria vaccine which blockades invasion of merozoites into human erythrocytes. Methods: Eight proteins derived from pl95 were expressed in E. coli, and purified by Ni-chelate affinity chromatography. The re folded proteins were labelled with colloidal gold. The labelled protein complexes were co-incubated with human erythrocytes separately and simultaneously, and the proteins were put into the culture supernatant of P- falciParum to observe their effect on invasion of merozoites into erythrocytes. Results: A fragment of p195, M6 (amino acid sequence: 384 - 595), was found to have the ability to bind human erythrocytes. M6 gold complexes showed no ability to bind erythrocytes treated with trypsin or neuraminidase. M6 was also found to have the ability to inhibit invasion of merozoites of P. falciparym into human erythrocytes. Conclusiou: A fragment of p195, M6, has the ability to bind human erythrocytes. The binding is dependent on sialic acid residues, and may be a prerequisite to recognition of erythrocytes by merozoites.
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