Fig. 1

Structure and conformation of FimH lectin domain and the FimH CDR-6xH variants. (a) The crystal structures of the loose (left, PDB ID: 4XO9, [14]) and tight (right, PDB ID: 1UWF, [15]) conformations of FimH are illustrated. Residues of the CDR loops that are mutated to histidine are in light blue (with those critical for mannose binding, N135 and D140, shown with sticks), and the remaining residues of the CDR loops are in dark blue. The rest of the lectin domain is white, the portion of the pilin domain shown is black, the bound ligand heptyl alpha-D-mannopyrannoside is orange, the residues mutated as “tightening substitutions” are pink (A188) and purple (Y64), and lastly, the epitope of mab21 is green (N29, N152-V156) [16]. (b) Binding of pili (CDR-6xH variants or wild-type CDR loops) was tested to mab824 (black bars) for expression and proper folding, and to mab21 (gray bars) to determine expression in the tight conformation. Nonspecific binding was subtracted from all measurements (n = 3, mean ± standard deviation)