title: Structure-Activity Studies of β-Hairpin Peptide Inhibitors of the Plasmodium falciparum AMA1-RON2 Interaction.
abstract: The interaction between apical membrane antigen 1 (AMA1) and rhoptry neck protein 2 (RON2) plays a key role in the invasion of red blood cells by Plasmodium parasites. Disruption of this critical protein-protein interaction represents a promising avenue for antimalarial drug discovery. In this work, we exploited a 13-residue β-hairpin based on the C-terminal loop of RON2 to probe a conserved binding site on Plasmodium falciparum AMA1. A series of mutations was synthetically engineered into β-hairpin peptides to establish structure-activity relationships. The best mutations improved the binding affinity of the β-hairpin peptide by ~7-fold for 3D7 AMA1 and ~14-fold for FVO AMA1. We determined the crystal structures of several β-hairpin peptides in complex with AMA1 in order to define the structural features and specific interactions that contribute to improved binding affinity. The same mutations in the longer RON2sp2 peptide (residues 2027-2055 of RON2) increased the binding affinity by >30-fold for 3D7 and FVO AMA1, producing KDvalues of 2.1nM and 0.4nM, respectively. To our knowledge, this is the most potent strain-transcending peptide reported to date and represents a valuable tool to characterize the AMA1-RON2 interaction.
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Geqing
authors.initials: G
authors.lastname: Wang
authors.affiliation: Biomedicine Discovery Institute, Department of Microbiology, Monash University, Wellington Rd, Clayton, Victoria 3800, Australia.
authors.forename: Nyssa
authors.initials: N
authors.lastname: Drinkwater
authors.affiliation: The Burnet Institute for Medical Research and Public Health, Melbourne, Victoria 3004, Australia.
authors.forename: Damien R
authors.initials: DR
authors.lastname: Drew
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Christopher A
authors.initials: CA
authors.lastname: MacRaild
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: David K
authors.initials: DK
authors.lastname: Chalmers
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Biswaranjan
authors.initials: B
authors.lastname: Mohanty
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: San Sui
authors.initials: SS
authors.lastname: Lim
authors.affiliation: Department of Biochemistry, La Trobe Institute for Molecular Science, La Trobe University, Bundoora, Victoria 3086, Australia.
authors.forename: Robin F
authors.initials: RF
authors.lastname: Anders
authors.affiliation: Biomedicine Discovery Institute, Department of Microbiology, Monash University, Wellington Rd, Clayton, Victoria 3800, Australia; The Burnet Institute for Medical Research and Public Health, Melbourne, Victoria 3004, Australia.
authors.forename: James G
authors.initials: JG
authors.lastname: Beeson
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Philip E
authors.initials: PE
authors.lastname: Thompson
authors.affiliation: Biomedicine Discovery Institute, Department of Microbiology, Monash University, Wellington Rd, Clayton, Victoria 3800, Australia.
authors.forename: Sheena
authors.initials: S
authors.lastname: McGowan
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia.
authors.forename: Jamie S
authors.initials: JS
authors.lastname: Simpson
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia. Electronic address: ray.norton@monash.edu.
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Norton
authors.affiliation: Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, 381 Royal Parade, Parkville, Victoria 3052, Australia. Electronic address: martin.scanlon@monash.edu.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Scanlon
mesh_terms: D000953:Antigens, Protozoan / Q000378:metabolism*; D000962:Antimalarials / Q000378:metabolism*; D018360:Crystallography, X-Ray; D008565:Membrane Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D008958:Models, Molecular; D050505:Mutant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000953:Antigens, Protozoan; D000962:Antimalarials; D008565:Membrane Proteins; D050505:Mutant Proteins; D010455:Peptides; D015800:Protozoan Proteins; C090555:ROP 2 protein, Toxoplasma gondii; C090077:apical membrane antigen I, Plasmodium
keywords: apical membrane antigen 1; malaria; peptide inhibitors; protein–peptide complex; structure-based ligand design