FIG. 3.

GST tag affects binding affinities of the fused P domain to HBGAs. (A) Western blot analysis of the GST-P fusion protein before (lanes 1 to 3) and after (lanes 5 to 7) thrombin cleavage using pooled antibodies against capsids of VA387, MOH, and Norwalk virus. The proteins before and after cleavage are at the same molar concentration. Lanes 1 and 5, P protein of VA387; lanes 2 and 6, P protein of MOH; lanes 3 and 7, P protein of Norwalk virus. Lane 4 is protein standard. (B to D) Binding curves of GST-P fusion protein before and after thrombin digestion. Data were averaged from at least three independent experiments. ▪, A antigen; ▴, B antigen; •, H antigen (type O saliva). (E) Binding curves of GST alone served as a negative control.