Related Experiment Videos
A naturally occurring gene encoding the major surface antigen precursor p190 of Plasmodium falciparum lacks
1Central Research Units, F. Hoffman-La Roche and Co. Ltd., Basel, Switzerland.
Abstract:
Plasmodium falciparum merozoites have variable surface proteins that are processed from a 190-kd precursor protein (p190). The gene encoding p190 exists in two allelic forms and cross-over events occurring mainly near the 5' end, combined with isolate-specific tripeptide repeats, contribute to its antigen diversity. We have sequenced a large portion of the p190 gene from the parasite isolate RO-33 (Ghana). Remarkably, the typical N-terminal tripeptide repeat structure is lacking. Apart from mutations in the variable parts, the gene appears identical to the MAD-20 allele (Papua, New Guinea). Southern blot analysis detects p190 genes similar to RO-33 in other parasite isolates independent of their geographical origin. The lack of p190 repeats in RO-33 eliminates the possibility that they are involved in host cell recognition or integration and restricts their function to immune escape.
Insights
The Plasmodium falciparum p190 gene, crucial for merozoite surface proteins, shows allelic variation. A Ghanaian isolate (RO-33) lacks N-terminal repeats, suggesting their role is primarily immune evasion rather than host cell interaction.
Area of Science:
- Malariology
- Molecular Parasitology
- Genomics
Background:
- Plasmodium falciparum merozoites utilize variable surface proteins derived from a 190-kd precursor protein (p190).
- Antigen diversity of p190 is influenced by allelic forms, recombination events, and isolate-specific tripeptide repeats.
Purpose of the Study:
- To sequence and analyze the p190 gene from the Plasmodium falciparum RO-33 isolate (Ghana).
- To investigate the structural characteristics and potential function of p190 repeats in parasite biology.
Main Methods:
- Gene sequencing of the p190 precursor protein in the RO-33 parasite isolate.
- Southern blot analysis to detect homologous p190 genes in other parasite isolates.
Main Results:
- The RO-33 isolate's p190 gene lacks the typical N-terminal tripeptide repeat structure found in other alleles.
- Apart from repeat variations, the RO-33 p190 gene is largely identical to the MAD-20 allele.
- Southern blot analysis confirmed the presence of RO-33-like p190 genes across various geographical parasite isolates.
Conclusions:
- The absence of N-terminal repeats in RO-33 suggests they are not essential for host cell recognition or integration.
- The findings restrict the primary function of p190 repeats to facilitating immune escape for Plasmodium falciparum.