FIG 3.

Analysis of the binding epitopes of anti-S2 mAbs. (A) The schematic diagram illustrated the design of the S2 truncation fragments. Fragments #1 and #2 contain a C-terminal His-tag. Fragments #3–12 contain an N-terminal sfGFP and a C-terminal His-tag. For easy reading of the WB results, the fragments that can be detected by mAbs S2-4D, S2-5D, and S2-8D are marked in red. (B–J) The binding activities of the control anti-His tag antibody, and mAbs S2-4D, S2-5D, and S2-8D against the S2 truncation fragments #1–12 were determined by WB analysis. (K–N) The recombinant sfGFP-S(1042-1167) (fragment #4) mutants with a series of individual alanine substitutions at residues 1137–1164 were expressed in E. coli, and the bacterial cell lysates (6 μg) were subjected to SDS-PAGE and WB analysis with mAbs S2-4D, S2-5D, and S2-8D to identify the critical antigenic determinants.