NMR solution structure of NBD94_483-502 of the nucleotide-binding domain of the Plasmodium yoelii reticulocyte-binding protein Py235

Invasion of the erythrocyte by the invasive form of the malaria parasite, the merozoite, is a complex process involving numerous parasite proteins. The reticulocyte-binding protein homologues (RH) family of merozoite proteins has been previously shown to play an important role in the invasion process. Previously, it has been shown that the RH proteins of Plasmodium yoelii, Py235, play a role as an ATP/ADP sensor. Binding of Py235 to the erythrocyte surface is increased in the presence of ATP, while ADP has an inhibitory effect. The sensor domain of Py235 is called NBD94 and the segment that has been shown to covalently bind the adenine nucleotide is made up by the residues ₄₈₃FNEIKEKLKHYNFDDFVKEE₅₀₂. Here, we report on the solution nuclear magnetic resonance structure of this peptide (NBD94_483-502) showing the presence of an α-helix between amino acid residues 485 and 491. The N- and C-terminal segments of the structure bend at tyrosine 493, a residue important for ATP binding. Importantly, erythrocyte-binding assays demonstrate that NBD94_483-502 can directly interfere with the binding of native Py235 to erythrocytes, suggesting a direct role of this region in erythrocyte binding. The data will provide the foundation for future studies to identify new compounds that directly interfere with the invasion process.