Apical membrane antigen 1 (AMA1) is a protein of the Plasmodium parasite that is involved in the formation of the moving junction during red blood cell invasion (1). Invasion inhibitory molecules like R1 peptide and anti-AMA1 antibodies target a conserved hydrophobic cleft on AMA1 and block the invasion process. Thus, AMA1 has become a target for drug development (2). Here we describe the application of solution NMR spectroscopy to study AMA1-small molecule interactions. Based on perturbations in specific chemical shifts in the NMR spectrum of AMA1, it is feasible to map the binding sites for ligand/small inhibitory molecules, facilitating the design of new drugs to treat malaria.
AMA1 is a high molecular mass (42 kDa) protein, making resonance assignments particularly challenging because of peak overlap. We have used different isotope labelling approaches (3, 4) and regular TROSY-based triple resonance NMR experiments to obtain residue-specific and sequential assignments, respectively. The results from chemical shift analysis of AMA1 and their importance in mapping the binding sites on AMA1 for small inhibitory molecules will be presented.