Fig 1.
Identification of peptide motifs with high affinity for the Stx B subunit using tetravalent peptide library screening. (A) The tetravalent peptide library was composed of tetravalent peptides with a polylysine core bifurcating at both ends with four randomized peptides. The peptide library for the first screening has a sequence of Met-Ala-X-X-X-R-X-X-X-Ala-U, in which U indicates aminohexanoic acid and X indicates any amino acid except Cys. Screening of the library was performed to identify tetravalent peptides that bound to 1BH but not to 1BH-F30A. For the second screening, a peptide library with fixed Args at positions 4 and 6 (RXR library) or fixed Args at positions 4 to 7 (XRR library) was used. Values in parentheses indicate the relative selectivities for the amino acids. Boldface letters indicate amino acids that were strongly selected. Each screening was performed twice; representative values are shown. (B) The kinetics of the binding of each tetravalent peptide with each identified binding motif to immobilized 1BH or 2BH was analyzed using the Biacore system. KD, dissociation constant; Rumax, maximum resonance unit. −, binding was not detected.