FIG 6.

TbpA-Tf binding ELISAs of TbpB⁻ strains. Whole, iron-stressed, TbpB-deficient gonococcal cells were applied to microtiter dishes for ELISAs with HRP-labeled Tf as the ligand. FA6905 (WT) served as the positive control, and FA6905 L3HA (L3HA) and the excess competitor hTf condition (Comp) served as negative controls. All data were normalized to FA6905. The data represent the mean values ± standard errors of at least three independent binding experiments. For all of the mutants compared to the positive control, the P values are <0.001, with the exception of the Q360K mutant, where the P value is <0.01. Statistics were calculated with the Student t test.