Cholera Toxin Structural Analyses

Ribostamycin, PDI, BfA, GM1, GSH, CTA, S-nitrosoglutathione, and anti-CTB antibodies were purchased from Sigma-Aldrich (St. Louis, MO). Bacitracin was purchased from Calbiochem (La Jolla, CA), CT was from List Biological Laboratories (Campbell, CA), and phosphate-buffered saline (pH 7.4) with 0.05% Tween 20 (PBST) was from Medicago (Uppsala, Sweden). ERp57, the anti-ERp57 antibody, and the anti-ERp72 antibody were from Abcam (Cambridge, MA). ERp72 and the anti-PDI antibody were purchased from Enzo Life Sciences (Farmingdale, NY). The anti-CTA1 monoclonal antibody 35C2 [52] (link) was a generous gift from Dr. Randall K. Holmes (University of Colorado School of Medicine). The pOLR130 plasmid encoding mature human PDI with an N-terminal His₆ tag [53] (link) was generously provided by Dr. Lloyd Ruddock (University of Oulu, Finland). Uniformly ¹³C-labeled ¹³C₆-_D-glucose and D₂O were purchased from Cambridge Isotope Laboratories (Andover, MA). Uniformly ¹³C-labeled CTA1-His₆ was produced as described in [7] (link) and purified as described in [22] (link).