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Plasmodium falciparum protein associated with the invasion junction contains a conserved oxidoreductase domain
D E Hudson-Taylor1, S A Dolan, F W Klotz
1Laboratory of Malaria Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Abstract:
The merozoite cap protein-1 (MCP-1) of Plasmodium falciparum follows the distribution of the moving junction during invasion of erythrocytes. We have cloned the gene encoding this protein from a cDNA library using a monoclonal antibody. The protein lacks a signal sequence and has no predicted transmembrane domains; none of the antisera reacts with the surfaces of intact merozoites, indicating that the cap distribution is submembranous. MCP-1 is divided into three domains. The N-terminal domain includes a 52-amino-acid region that is highly conserved in a large family of bacterial and eukaryotic proteins. Based on the known functions of two proteins of this family and the pattern of amino acid conservation, it is predicted that this domain may possess oxido-reductase activity, since the active cysteine residue of this domain is invariant in all proteins of the family. The other two domains of MCP-1 are not found in any other members of this protein family and may reflect the specific function of MCP-1 in invasion. The middle domain is negatively charged and enriched in glutamate; the C-terminal domain is positively charged and enriched in lysine. By virtue of its positive charge, the C-terminal domain resembles domains in some cytoskeleton-associated proteins and may mediate the interaction of MCP-1 with cytoskeleton in Plasmodium.
Insights
Merozoite cap protein-1 (MCP-1) in Plasmodium falciparum is submembranous and may have oxido-reductase activity. Its unique domains suggest specific roles in erythrocyte invasion and potential cytoskeleton interaction.
Area of Science:
- Malariology
- Molecular Parasitology
- Protein Biochemistry
Background:
- Plasmodium falciparum merozoites invade erythrocytes, a critical step in malaria pathogenesis.
- The moving junction complex is essential for this invasion process.
- Understanding merozoite proteins involved in invasion is key to developing antimalarial strategies.
Purpose of the Study:
- To clone and characterize the merozoite cap protein-1 (MCP-1) from Plasmodium falciparum.
- To investigate the localization and potential functions of MCP-1 during erythrocyte invasion.
Main Methods:
- Cloning of the MCP-1 gene using a monoclonal antibody and a cDNA library.
- Bioinformatic analysis to predict protein domains and functions.
- Immunological assays to determine protein localization (submembranous vs. surface).
Main Results:
- MCP-1 was cloned and found to lack signal sequences and transmembrane domains, indicating submembranous localization.
- The N-terminal domain shows high conservation and predicted oxido-reductase activity.
- Unique middle (negatively charged) and C-terminal (positively charged) domains were identified, suggesting specific roles in invasion and cytoskeleton interaction.
Conclusions:
- MCP-1 is a submembranous protein involved in Plasmodium falciparum invasion.
- Its conserved N-terminal domain may possess enzymatic activity.
- The distinct C-terminal domain likely mediates interactions with the cytoskeleton, contributing to invasion mechanics.