Ig 1–2 and Ig 10–11 dimerize and induce ER voids upon overexpression. (A) SDS-PAGE/Coomassie staining of constructs obtained from preparative SEC. (B and C) SEC profiles of recombinantly purified Ig 1–2 and Ig 10–11 on a HiLoad Superdex 75 pg. (D and E) ITC-binding studies of constructs used in A–C with dissociation constants (K_D) and binding stoichiometry (n) indicated. n = 3 biological replicates. (F) Representative U2OS cells immunostained for the ER marker calreticulin and for either Ig 1–2-HA or Ig 10–11-FLAG expression. (G) Plot of mean void area relative to ER area per cell scored for the indicated construct expression. N = 113 untransfected cells (Ctrl), N = 103 Ig 10–11-FLAG–transfected cells, N = 105 WT Ig 1–2-HA–transfected cells, and N = 107 3-Mut Ig 1–2-HA–transfected cells from. Error bars denote ± SD. Statistical analyses were performed using an ordinary one-way ANOVA test; ****P < 0.0001, **P < 0.01, and ns, not significant. Scale bars, 10 μm. Source numerical data and unprocessed blots are available in source data. Source data are available for this figure: SourceData F3.