A tandemly repeated sequence determines the binding domain for an erythrocyte receptor binding protein of P. falciparum.

Erythrocyte invasion by the malarial merozoite is a receptor-mediated process, an obligatory step in the development of the parasite. The Plasmodium falciparum protein GBP-130, which binds to the erythrocyte receptor glycophorin, is shown here to encode the binding site in a domain composed of a tandemly repeated 50 amino acid sequence. The amino acid sequence of GBP-130, deduced from the cloned and sequenced gene, reveals that the protein contains 11 highly conserved 50 amino acid repeats and a charged N-terminal region of 225 amino acids. Binding studies on recombinant proteins expressing different numbers of repeats suggest that a correlation exists between glycophorin binding and repeat number. Thus, a repeat domain, a common feature of plasmodial antigens, has been shown to have a function independent of the immune system. This conclusion is further supported by the ability of antibodies directed against the repeat sequence to inhibit the in vitro invasion of erythrocytes by merozoites.