Schematic map of the primary structure of PfRON3. The PfRON3 protein contains 2215 amino acids with a calculated molecular mass of 263.15 kDa. A predicted signal peptide (SP, residues 1 to 20), three transmembrane regions (TM, residues 250 to 272, 276 to 298 and 551 to 573), and a coiled-coil region (aa 1822 to 1847) are indicated with dark, grey and slashed bars. The regions (I, II, III, and IV) corresponding to the four recombinant proteins generated are indicated underneath. The molecule is putatively divided into A, B and C regions based on the location of SP and TM regions (also see the Additional file 2).