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Characterization of the MSP-1 Protein in Field Samples of Plasmodium falciparum and its Homology to the Plasmodium Vivax MSP-1 Protein
Merozoite surface protein-1 (MSP-1) is one of the several proteins on the surface of the asexual merozoite of malaria parasites. It undergoes a two stage proteolytic cleavage to form a C-terminal 19- kDa fragment or PfMSP119 that is used for red blood cell invasion. A homologue of PfMSP-119 of Plasmodium falciparum called PvMSP-119 has been identified in Plasmodium vivax. Recently, attention has been focused on this C-terminal cysteine-rich region as an important determinant of haplotypes that characterize the malaria parasite in endemic areas. In this study, sequence specific primers were used to determine the PfMSP-119 haplotypes from field samples and PvMSP-119 haplotypes from both field and Aotus adapted parasites. 163 PfMSP-119 samples from Kisumu-Kenya were polymerase chain reaction (PCR) typed at position 1644 in the first epidermal growth factor (EGF)-like domain followed by sequencing of a random selection of positive samples so as to evaluate molecular changes at positions 1691, 1700 and 1701 in the second EGF-like domain. 121 selected samples gave bands, with 80% typing as GAA (E) and 20% as CAA (Q) at position 1644. From computer-alignment sequences, samples 96B216 confirmed as the Uganda-PA haplotype (E-KNG), 96B209 as the PfMAD20 haplotype (E-TSR), 96B208 as the PfK1/Wellcome haplotype (Q-KNG), 96B183 as the Uganda-PA haplotype (E-KNG) and 96B017 as the E-TSG haplotype. Next, genotyping and sequence analyses of the PvMSP-119 fragment against reference sequences from GenBank demonstrated isolates as belonging to either one or the other of two parental haplotypes identified as Belem and Sal-1 strains. Comparison of PfMSP-119 and PvMSP-119 fragments demonstrated highly conserved cysteine amino acids in the two EGF-like domains.
Merozoite Surface Protein-1 (MSP-1), Polymerase Chain Reaction (PCR), Plasmodium falciparum, Epidermal Growth Factor (EGF), Genbank, Plasmodium Vivax, Malaria Parasite.
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