The FaeG-binding sites in the APN protein. A Array of overlapping APN peptides. We used a membrane spotted with peptides (Additional file 2) that spanned the entire amino acid sequence of APN for incubation in either natural F4 fimbrial proteins or fusion FaeG proteins. The image of the membrane shows the reactivity at each spot. The spot with the strongest signal are set the standard (100% intensity), all other intensity values as a relative percentage of this standard. We only considered spots with intensities > 30% as positive. B ELISA assays. We coated APN protein and 13 peptides of the APN on ELISA plates, and then used the coated plates to test the binding activity of the APN with the F4 fimbriae and the FaeG peptides, the APN protein as a positive control. The data presented here are the average of the three experiments and shown as mean ± standard deviations (*p < 0.05, **p < 0.01).