Fig. 4.

Interaction of OxyA_kis and OxyC_kis with the X-domain from the kistamicin NRPS. a SDS-PAGE of OxyA_kis (44.9 kDa), OxyC_kis (48.8 kDa), the X_kis-domain (52.0 kDa) and PCP-X_kis (60.2 kDa). Native PAGE of the X_kis-domain and PCP-X_kis didomain in isolation and after co-incubation with OxyA_kis and OxyC_kis visualised both with Coomassie blue stain (b) and using UV visualisation (c, following prior FITC labelling of the X_kis-domain and the PCP-X_kis didomain). d Representative ITC isotherm data for interactions between (d) OxyA_kis and (e) OxyC_kis with the X_kis-domain. The upper panels represent baseline-corrected power traces; by convention, negative power corresponds to exothermic binding. The middle panels represent the integrated heat data fitted to the single binding sites model in SEDPHAT⁵⁸, with figures produced using GUSSI⁵⁹. The bottom panels show the residues of the fit with error bars are standard error in the integration of the peaks as calculated by NITPIC (n = 1)⁵⁷. f Binding affinities of OxyA_kis and OxyC_kis with the X_kis-domain. Affinities were determined by ITC at 25 °C with stirring at 300 rpm. 68.3% confidence intervals (1 Std. Dev.) are given in parentheses for K_a and K_d as calculated from a single titration. Source data are provided as a Source Data file