Surface proteins of Plasmodium falciparum merozoites binding to the erythrocyte receptor, glycophorin.

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Abstract
This work identified a receptor or ligand molecule on the P. falciparum merozoite surface that mediates binding to the human erythrocyte. A fraction containing the sialoglycoproteins was coupled to an acrylamide matrix and incubated with metabolically labeled merozoites. A merozoite protein of 155 kilodaltons (kD) that labeled prominently with [3H]glycine bound to glycophorin. A minor protein of 130 kD also bound. Both proteins are rich in proline and glycine, poor in methionine, and may be related. The proteins are also stable to heating to 100.degree. C for 10 min. Immuno-EM demonstrated that the 155 kD and 130 kD proteins are located on the merozoite surface coat. The antibodies significantly inhibited merozoite invasion into erythrocytes and also binding of the proteins to the glycophorin-matrix. The specific binding of the 155-kD and 130-kD proteins to the erythrocyte receptor and the demonstration that they are located on the merozoite surface suggest they could be receptor proteins that mediate binding of the merozoite to the erythrocyte surface.