Comparison of surface properties. (a) Hydrophobicity surface presentations for MtbDsbA and EcDsbA. Surface colourings are mapped to the Kyte–Doolittle hydrophobicity scale from purple (most hydrophilic) to white to tan (most hydrophobic). The MtbDsbA structure is shown (left) with the modelled VKOR peptide (VPSCNV) and crystallographically identified artificial ligand 1,4-dioxane (see text and Supplementary Fig. S4 for details). The EcDsbA–EcDsbB complex structure is shown on the right (PDB entry 3e9j
; Malojcić et al., 2008). For clarity only the periplasmic loop segment `PFATCDF' of EcDsbB is shown. Electrostatic surface comparisons of (b) MtbDsbA, (c) the hypothetical model of PknE DsbA and (d) EcDsbA. Electrostatic surface potential is contoured between −6 (red) and +6 (blue) kT/e. The homology model of PknE (template based on MtbDsbA and BsDsbA) was prepared in MODELLER (Eswar et al., 2006) and atomic clashes were minimized in Chiron (Ramachandran et al., 2011).