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Cloning of the Plasmodium vivax Duffy receptor
X D Fang1, D C Kaslow, J H Adams
1Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892.
Abstract:
Plasmodium vivax and Plasmodium knowlesi merozoites invade only Duffy blood group-positive human erythrocytes. Soluble P. vivax and P. knowlesi merozoite proteins of 135 kDa bind specifically to Duffy blood group determinants. The gene encoding a member of the Duffy receptor gene family of P. knowlesi has been cloned. We report here the molecular cloning of the presumptive Duffy receptor gene of P. vivax, using the P. knowlesi gene as a probe. There is a single gene in P. vivax which codes for a protein of 1115 amino acids. The deduced amino acid sequence predicts a putative signal sequence at the amino-terminus and a transmembrane region followed by 45 amino acids at the carboxy-terminus. The three introns found at the 3' end of the P. knowlesi gene were conserved in P. vivax, including high homology for the sequences of the introns. Comparison of the portion of the proteins amino to the transmembrane region between P. vivax and the partial sequence of P. knowlesi indicated at least three domains. Two homologous regions were separated by a non-homologous region. The cysteines in the homologous regions were conserved in number and position, indicating that the folding is similar and suggesting that these regions may be the Duffy blood group binding domains. In both P. vivax and P. knowlesi, the non-homologous region is hydrophilic and proline-rich, although the position of the prolines is not conserved. As prolines tend to stiffen a protein, this region may act as a 'hinge region' similar to those in the immunoglobulin gene family.
Insights
Researchers cloned the Duffy receptor gene from Plasmodium vivax, crucial for malaria parasite invasion of human red blood cells. This finding advances understanding of Plasmodium vivax and Plasmodium knowlesi interactions with the Duffy blood group.
Area of Science:
- Molecular biology
- Parasitology
- Genetics
Background:
- Plasmodium vivax and Plasmodium knowlesi merozoites infect only Duffy blood group-positive erythrocytes.
- Soluble merozoite proteins from these parasites bind to Duffy blood group determinants.
Purpose of the Study:
- To molecularly clone the presumptive Duffy receptor gene of Plasmodium vivax.
- To compare the Duffy receptor gene and protein structure between P. vivax and P. knowlesi.
Main Methods:
- Utilized the cloned P. knowlesi Duffy receptor gene as a probe for molecular cloning in P. vivax.
- Deduced amino acid sequence and analyzed protein structure, including signal sequence, transmembrane region, and conserved domains.
- Compared intron sequences and protein homology between P. vivax and P. knowlesi.
Main Results:
- Successfully cloned a single gene in P. vivax encoding a 1115-amino acid protein.
- Identified conserved introns and high homology in intron sequences between P. vivax and P. knowlesi.
- Discovered conserved cysteine residues in homologous protein domains, suggesting Duffy binding functions, and a hydrophilic, proline-rich non-homologous region potentially acting as a hinge.
Conclusions:
- The cloned P. vivax gene codes for a protein with structural similarities to the P. knowlesi Duffy receptor.
- Conserved domains and cysteine residues indicate potential Duffy blood group binding sites.
- The proline-rich region may function as a hinge, analogous to immunoglobulin gene families.