Structural comparison of MtbDsbA. (a) The crystal structure of MtbDsbA (left) is compared with the prototypical EcDsbA (right; PDB entry 1fvk
; Guddat et al., 1998). Catalytic/noncatalytic cysteine residues are shown as light grey spheres. The noncatalytic structural disulfide of MtbDsbA is absent in EcDsbA. Helix H8 appears to be unique to MtbDsbA. The orientation of helix H5 dramatically varies in these two proteins. Gly204 breaks the hydrogen-bonding pattern in the middle of helix H6 of MtbDsbA (helix H6 is kinked in MtbDsbA compared with EcDsbA). MtbDsbA appears to be much smaller in size than EcDsbA in this orientation. However, the molecular surface areas of MtbDsbA (8208 Å2) and EcDsbA (8670 Å2) are comparable. The intramolecular interaction of helix H1 with the C-terminal region of (b) MtbDsbA, (c) EcDsbA (PDB entry 1fvk
; Guddat et al., 1998) and (d) VcDsbA (PDB entry 1bed
; Hu et al., 1997) is also shown. For (b), (c) and (d) the backbone colour is set to the temperature factor from the PDB. The side chains of interfacing residues identified by PISA (Protein Interfaces, Surfaces and Assemblies; Krissinel & Henrick, 2007) analysis are shown as sticks. Catalytic and noncatalytic cysteines are shown as grey spheres.