Native Protein Separation and Oligomeric State Determination

The hrCN PAGE protocol was adapted from Lemaire et al. (2018) (link). Glycerol was added to the sample at a final amount of 20% (v/v). Ponceau S at a final concentration of 0.001% (w/v) served as a marker to follow the migration. The buffer composition for the electrophoresis cathode was the following: 50 mM tricine, 15 mM Bis-Tris/HCl, pH 7.0, 0.05% (w/v) sodium deoxycholate, 2 mM DTT, and 0.01% (w/v) dodecyl maltoside, whilst the anode buffer contained 50 mM Bis-Tris/HCl, PH 7.0, 2 mM DTT. An 8–15% linear polyacrylamide gradient gel was used, and electrophoresis was run under a N₂/CO₂ (90:10%) atmosphere with a constant 40 mA current (PowerPac^™ Basic Power Supply, Bio-Rad). After electrophoresis, protein bands were visualised with Ready Blue^™ Protein Gel stain (Sigma Aldrich, Hamburg, Germany). The native protein ladder used is NativeMark^™ Unstained Protein Standard (Thermo Fischer Scientific, Driesch, Germany).
The determination of the oligomeric state by gel filtration was performed in triplicate on a Superose 6 Increase 10/300 GL (GE Healthcare, Munich, Germany) in 25 mM Tris/HCl pH 7.6, 2 mM DTT, 10% (v/v) glycerol at a flow rate of 0.4 ml/min, and in an anaerobic Coy tent containing an N₂/H₂ (97:3%) atmosphere. High molecular weight range gel filtration calibration kit (GE Healthcare, Munich, Germany) was used as the protein standard.