Western blot analysis of recombinant GST (28 kDa) and GST - fusion protein (61 kDa) were resolved by SDS - PAGE , transferred to PVDF membrane and probed with GST monoclonal antibody, clone 1E5 (1 : 1000) (Cat # MAB1132) . Proteins were visualized using a goat anti - mouse secondary antibody conjugated to HRP and an ECL detection system. Arrows indicate GST and GST - fusion proteins (20 ng) .