orals 5th Asia-Pacific NMR Symposium 2013

Molecular insights into the interaction between malaria antigen AMA1 and an invasion-inhibitory peptide (#218)

Geqing Wang 1 , Chris A. MacRaild 1 , Biswaranjan Mohanty 1 2 , Robin F. Anders 3 , Jamie S. Simpson 1 , Martin J. Scanlon 1 2 , Raymond S. Norton 1
  1. Monash Institute of Pharmaceutical Science, Parkville, VIC, Australia
  2. ARC Centre of Excellence for Coherent X-ray Science, Monash University, Melbourne, Australia
  3. Biochemistry, La Trobe University, Melbourne, VIC, Australia

Erythrocyte invasion by malaria parasites relies on the interaction between Apical Membrane Antigen 1 (AMA1) and the Rhoptry Neck protein (RON) complex 1. As this invasion mechanism is highly conserved in all apicomplexan parasites, chemical intervention in this protein-protein interaction represents a promising therap1 eutic approach to combat malaria infection. A well-defined, highly conserved hydrophobic cleft on AMA1, which was identified as a RON2 binding site 2, is favourable for designing small-molecule inhibitors to bind and block the erythrocyte invasion. In addition, targeting conserved residues by small molecules will be more likely to produce an anti-malarial with broad strain specificity and less susceptibility to drug resistance.

The development of small-molecule inhibitors can be aided by a molecular probe, which enables the detailed characterization of inhibitory interaction on the conserved hydrophobic cleft and serves as a pharmacophore for structure-based drug design. A 20-mer peptide designated R1 (VFAEFLPLFSKFGSRMHILK), which displays high binding affinity for P. falciparum 3D7 AMA1 and inhibits erythrocyte invasion in vitro strain-specifically 3, is employed in this study. Here we established the expression and purification protocol for isotopically labelled R1 and AMA1, and investigate the AMA1-R1 interaction by Nuclear Magnetic Resonance (NMR) spectroscopy. Using Surface Plasmon Resonance (SPR), we identified the minimal binding construct of R1 by a series of truncations and revealed the key AMA1-interacting residues along this part of peptide by alanine scan. The truncation, mutagenesis and structural information presented here will provide a valuable starting point for small-molecule inhibitor design and potentially leads to a new class of anti-malarial drug.

  1. Richard D, et al. (2010) Interaction between Plasmodium falciparum apical membrane antigen 1 and the rhoptry neck protein complex defines a key step in the erythrocyte invasion process of malaria parasites. J Biol Chem 285(19):14815-14822.
  2. Tonkin ML, et al. (2011) Host cell invasion by apicomplexan parasites: insights from the co-structure of AMA1 with a RON2 peptide. Science 333(6041):463-467.
  3. Harris KS, et al. (2009) Rapid optimization of a peptide inhibitor of malaria parasite invasion by comprehensive N-methyl scanning. J Biol Chem 284(14):9361-9371.