Figure 6

CaCl ₂ titration and surface potential map of ChaB. (A) Summary of the perturbations of CaCl₂ on the backbone ¹H-¹⁵N chemical shifts of ChaB. The change in chemical shifts (determined from a weighted vector sum of ¹H and ¹⁵N ppm deviations) are mapped onto the structure of ChaB using a colour gradient from blue, to red to yellow, where yellow is the largest perturbation and blue the smallest. Residues that could not be analyzed such as overlapping residues or residues that do not exhibit NH resonances are coloured grey. (B) Potential map of the surface of ChaB calculated using MOLMOL [35] shown in the same orientation as (A). Residues most perturbed by Ca²⁺ cluster around a highly negatively charged patch on the ChaB surface comprising a flexible loop.