FIG. 6.

Effects of peptide chain length on binding to OppA proteins. Competitive binding assays were performed with lysine-containing peptides of various lengths [e.g., (K)2, which represents KK]. The abilities to compete for binding were compared for A1-10 and OppA-1 (black bars), A2-8 and OppA-2 (white bars), and A3-3 and OppA-3 (gray bars). Assays were performed at pH 7.0 for OppA-1 and OppA-3 and at pH 5.0 for OppA-2. In each assay, a 20 μM concentration of amino acid or peptide was used as a competitor. Experiments were performed a minimum of three times in duplicate; error bars represent standard errors of the means.