Lectin-Like Bacteriocins from Pseudomonas spp. Utilise D-Rhamnose Containing Lipopolysaccharide as a Cellular Receptor
Figure 3
Pyocin L1 shows specificity for d-rhamnose compared with d-mannose.
(A) ITC binding isotherm of d-rhamnose (50 mM) titrated into pyocin L1 (100 µM). Weakly saturable heats were observed, indicative of binding with modest affinity (Kd ∼5–10 mM). (B) ITC binding isotherm of d-mannose (50 mM) titrated into pyocin L1 (100 µM). Small-weakly saturable heats were observed, indicative of very weak interaction (Kd ∼50 mM). Titration of monomeric sugars into 15N-labelled pyocin L1, monitored using 1H-15N HSQC NMR spectroscopy. Shifts within spectra were converted to chemical shift perturbation (CSP) values using equation Δppm = √ [ΔδHN+(ΔδN*αN)2]. CSP values are plotted against sugar concentration in (C) and (E) and visualised in (D) and (F). Peak positions, which correspond to backbone amide signals, at selected sugar concentrations (blue: no sugar, green: 60 mM, red: 100 mM) are shown. Perturbation of peak position (ppm) is indicative of association between ligand and protein molecules in solution.