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A tandemly repeated sequence determines the binding domain for an erythrocyte receptor binding protein of P.
Abstract:
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.
Insights
The Plasmodium falciparum protein GBP-130
Area of Science:
- Malariology
- Parasitology
- Molecular Biology
Background:
- Malarial merozoite invasion of erythrocytes is crucial for parasite development.
- Protein-receptor interactions mediate this essential step.
- Plasmodium falciparum utilizes specific proteins to bind erythrocytes.
Purpose of the Study:
- To identify the functional domain of Plasmodium falciparum GBP-130 responsible for erythrocyte binding.
- To investigate the role of repeat sequences within GBP-130.
- To determine if the binding domain has a function independent of immune responses.
Main Methods:
- Gene cloning and sequencing of Plasmodium falciparum GBP-130.
- Expression and purification of recombinant GBP-130 proteins with varying repeat numbers.
- Erythrocyte binding assays using recombinant proteins.
- In vitro inhibition assays using antibodies against repeat sequences.
Main Results:
- The erythrocyte binding site of GBP-130 is located within a domain of tandemly repeated 50 amino acid sequences.
- GBP-130 contains 11 conserved 50 amino acid repeats.
- Glycophorin binding correlates with the number of repeat units.
- Antibodies against the repeat sequence inhibit merozoite invasion.
Conclusions:
- The repeat domain of GBP-130 is essential for glycophorin binding and erythrocyte invasion.
- This functional domain operates independently of the host immune system.
- GBP-130's repeat domain plays a critical role in the Plasmodium falciparum life cycle.
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