Figure 5.

Small-angle X-ray scattering data for α-DsbA2ΔN and FL α-DsbA2. (a) Measured scattering data for α-DsbA2ΔN (red; multiplied by a factor of ten for clarity) and FL α-DsbA2 (blue). The scattering profiles of rigid-body models are shown as solid black lines overlaid on the scattering data for α-­DsbA2ΔN [χ² = 3.88; CorMap test (Franke et al., 2015 ▸), 294 points, C = 66, P = 0.000] and FL α-DsbA2 (χ² = 1.37; CorMap test, 320 points, C = 13, P = 0.037). Inset: Guinier plot for α-DsbA2ΔN (red; R ² = 0.999) and FL α-DsbA2 (blue; R ² = 1.000). (b) The pair-distance distribution function, p(r), derived from the scattering data is indicative of a globular structure with a maximum dimension of ∼63 Å for α-DsbA2ΔN (red) and ∼87 Å for FL α-DsbA2 (blue). For reference, the experimental p(r) for trimeric PmScsC is also shown (dotted line). (c) Probable shape of α-DsbA2ΔN (monomeric) obtained from the filtered average of 16 dummy-atom models (red envelope): χ² = 1.038 ± 0.002; NSD = 0.446 ± 0.021; resolution = 17 ± 2 Å. (d) Probable shape of FL α-DsbA2 obtained from the filtered average of nine dummy-atom models (blue envelope): χ² = 1.202 ± 0.003; NSD = 0.602 ± 0.027; resolution = 30 ± 2 Å. The images in (c) and (d) were generated using PyMOL (v.1.2r3pre; Schrödinger), where the grey shapes represent the total volume encompassed by the aligned dummy-atom models and the corresponding rigid-body model is shown aligned with the filtered model (flexible regions are represented by chains of black spheres).