Fig. 3.
PgpB interacts with PBP1B but not with PBP1A. (A) Oligohistidine tagged PgpB (PgpB-ht) and PBP1A alone, or both proteins together were incubated with chemical cross-linker and followed by pull-down to Ni-NTA beads. PgpB-ht did not interact with PBP1A. PgpB-ht did pull down PBP1B to Ni-NTA beads in the presence (B) or absence (C) of chemical cross-linker. Lanes labelled with A correspond to samples applied to the Ni-NTA beads and E to the elution. (D) PBP1A, PBP1B or no protein were immobilized on a sensor chip with bound ampicillin. PgpB-ht was applied at concentrations of 2, 1, 0.5, 0.25 or 0.125 µM. PgpB-ht bound to immobilised PBP1B but not to PBP1A or the control surface. (E) Analysis of the titration data in panel D using a 1:1 binding model yields an apparent KD of 1.05 ± 0.06 µM (three independent experiments).