title: Identification of key residues involved in fibril formation by the conserved N-terminal region of Plasmodium falciparum merozoite surface protein 2 (MSP2).
abstract: Merozoite surface protein 2 (MSP2) from the human malaria parasite Plasmodium falciparum is expressed as a GPI-anchored protein on the merozoite surface. MSP2 is assumed to have a role in erythrocyte invasion and is a leading vaccine candidate. Recombinant MSP2 forms amyloid-like fibrils upon storage, as do peptides corresponding to sequences in the conserved N-terminal region, which constitutes the structural core of fibrils formed by full-length MSP2. We have investigated the roles of individual residues in fibril formation and local ordered structure in two peptides, a recombinant 25-residue peptide corresponding to the entire N-terminal domain of mature MSP2 and an 8-residue peptide from the central region of this domain (residues 8-15). Both peptides formed fibrils that were similar to amyloid-like fibrils formed by full-length MSP2. Phe11 and Ile12 have important roles both in stabilising local structure in these peptides and promoting fibril formation; the F11A and I12A mutants of MSP2(8-15) were essentially unstructured in solution and fibril formation at pH 7.4 and 4.7 was markedly retarded. The T10A mutant showed intermediate behaviour, having a less well defined structure than wild-type and slower fibril formation at pH 7.4. The mutation of Phe11 and Ile12 in MSP2(1-25) significantly retarded but did not abolish fibril formation, indicating that these residues also play a key role in fibril formation by the entire N-terminal conserved region. These mutations had little effect on the aggregation of full-length MSP2, however, suggesting that regions outside the conserved N-terminus have unanticipated importance for fibril formation in the full-length protein.
authors.affiliation: The Walter & Eliza Hall Institute of Medical Research, 1G Royal Parade, Parkville 3052, Australia.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Yang
authors.forename: Christopher G
authors.initials: CG
authors.lastname: Adda
authors.forename: Christopher A
authors.initials: CA
authors.lastname: MacRaild
authors.forename: Andrew
authors.initials: A
authors.lastname: Low
authors.forename: Xuecheng
authors.initials: X
authors.lastname: Zhang
authors.forename: Weiguang
authors.initials: W
authors.lastname: Zeng
authors.forename: David C
authors.initials: DC
authors.lastname: Jackson
authors.forename: Robin F
authors.initials: RF
authors.lastname: Anders
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Norton
mesh_terms: D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry; D000953:Antigens, Protozoan / Q000737:chemistry* / Q000235:genetics; D017124:Conserved Sequence; D006863:Hydrogen-Ion Concentration; D020125:Mutation, Missense; D010446:Peptide Fragments / Q000737:chemistry*; D010963:Plasmodium falciparum / Q000737:chemistry*; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry* / Q000235:genetics
chemical_list: D000682:Amyloid; D000953:Antigens, Protozoan; D010446:Peptide Fragments; D015800:Protozoan Proteins; C065974:merozoite surface protein 2, Plasmodium