Figure 1
Deglycosylation and crystallization of the apo CTLA-4 homodimer. (a) Coomassie-stained SDS–polyacrylamide gel run under reducing conditions showing undigested (−) and Endo H-digested (+) CTLA-4ex expressed in wild-type and mutant CHO cells with and without glycan-processing inhibitors. Samples in the left and right lanes marked with (+) were Endo H-digested for 1 and 3 h, respectively, in order to confirm that after 1 h the reaction had proceeded to completion. Sample 1, CHO-K1 cells only; sample 2, CHO-K1 cells with 1.5 mM NB-DNJ; sample 3, CHO-K1 cells with 10 µM kifunensine; sample 4, CHO Lec3.2.8.1 cells only; sample 5, CHO Lec3.2.8.1 cells with 0.5 mM NB-DNJ. In (b) crystals were grown in 25%(w/v) polyethylene glycol 1500 in 0.1 M sodium propionate/sodium cacodylate/Bis-Tris propane buffer pH 6.0 (Molecular Dimensions). These crystals were ∼100 × 100 × 100 µm in size. The crystal shown in (c) was grown in 0.2 M ammonium acetate, 25%(w/v) polyethylene glycol 1500, 0.1 M Bis-Tris pH 5.5 (Hampton Research). This crystal was ∼100 × 200 × 100 µm in size. |