Erythrocyte-binding activity of PfRON3 proteins. (A) SDS-PAGE analysis of purified GST-tagged PfRON3 proteins. The purified RON3-I (52 kDa), RON2-II (54 kDa), RON3-III (74.1 kDa), RON3-IV (55.7 kDa) and GST (26 kDa) proteins were resolved in 12% SDS-PAGE gels and stained with Coomassie brilliant blue R-250 are shown. (B) Western blot analysis of the erythrocyte-binding activity of the recombinant GST-tagged PfRON3 proteins. The proteins were mixed with human erythrocytes separately and the binding was subsequently detected with a GST-specific mAb. The results show that only the recombinant PfRON3-I protein could bind to human erythrocytes. (C) Detection of the binding of the native PfRNO3 with human red blood cells. Soluble parasite proteins were incubated with human RBC and the binding of PfRON3 with RBC was detected with a specific antibody in Western-blot. The antibody only recognized the protein (PfRON3) (lane 2), but not reacted with any protein of RBC (lane 1).