Figure 2.

Structure and function of refolded PDI. (A-B) CD spectra for rPDI (A) or oPDI (B) were measured at 25°C (black line) before heating rPDI to 65°C and oPDI to 70°C. Spectra were measured again after 10 min at elevated temperature (dotted line) and after cooling back to 25°C (grey line). (C) oPDI and rPDI samples were left at room temperature or heated to the indicated temperatures for 10 min. After cooling to room temperature, each sample was added to a 96-well plate coated with CT. Loss of the CTA1 subunit due to PDI-driven CT disassembly was subsequently detected by ELISA. Final values were calculated based on the maximum CTA1 signal from CT holotoxin incubated in the absence of PDI, as detailed in the Materials and Methods. Error bars report standard error of the means from at least five independent experiments per condition, each with four replicate samples. All values represent statistically significant differences from the rPDI control (Student's t test, p < 0.05).