SDS-PAGE and Native PAGE Analysis

For SDS-PAGE, 4 μg of protein samples was loaded on to a 10% TGX™ FastCast™ (Bio-Rad Laboratories, Hercules, CA, USA) polyacrylamide gel. Protein samples were prepared with 4X sample loading buffer (Bio-Rad Laboratories) for reducing conditions and with Pierce™ LDS sample buffer, non-reducing (4X) (Thermo Fisher Scientific) for non-reducing conditions. For native PAGE, protein samples were loaded on to a NativePAGE™ 4 to 16% Bis-Tris Mini Protein Gels (Thermo Fisher Scientific) with NativeMark™ Unstained Protein Standard (Thermo Fisher Scientific) and separated at 125 V for 2 h. A recombinant prolyl-4-hydroxylase (homodimer, 49.2-kDa) was used as the protein standard [22 (link)].