title: The alanine-rich heptad repeats are intact in the processed form of Plasmodium falciparum MSP3.
abstract: The potential of Plasmodium falciparum merozoite surface protein 3 as a component of an asexual-stage malaria vaccine is currently being assessed. The precursor form of MSP3 undergoes cleavage during schizogony to generate a mature processed form. It is unknown if this cleavage event is necessary for MSP3 function, but it may be an important consideration for assessing and developing MSP3 as an asexual-stage vaccine candidate. We have therefore determined the cleavage site in MSP3 by sequencing the N-terminus of the processed form of MSP3, which was isolated from parasite material. The position of the cleavage site indicates that the processed form of MSP3 retains the three blocks of alanine-rich heptad repeats, which are predicted to provide the structural framework for an intramolecular coiled-coil. The cleavage-site motif has many features in common with the published cleavage sites of MSP1(30), MSP6(36), and MSP7(22), which are all located on the merozoite surface and are implicated in the erythrocyte invasion process. The common cellular location and similar cleavage-site motifs suggest that these merozoite proteins may be cleaved by the same or related proteases.
authors.affiliation: Infection and Immunity Division, The Walter and Eliza Hall Institute of Medical Research, Melbourne, Vic. 3050, Australia.
authors.forename: J Andrew
authors.initials: JA
authors.lastname: Pearce
authors.forename: Anthony N
authors.initials: AN
authors.lastname: Hodder
authors.forename: Robin F
authors.initials: RF
authors.lastname: Anders
mesh_terms: D000409:Alanine / Q000737:chemistry*; D000818:Animals; D000953:Antigens, Protozoan / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D015151:Immunoblotting; D008969:Molecular Sequence Data; D010963:Plasmodium falciparum / Q000737:chemistry*; D015800:Protozoan Proteins / Q000737:chemistry*; D020449:Repetitive Sequences, Amino Acid; D016415:Sequence Alignment
chemical_list: D000953:Antigens, Protozoan; D015800:Protozoan Proteins; C089133:merozoite surface protein 3, Plasmodium; D000409:Alanine