A Cleavage of eDHFR-HA (1.5 mg/ml) as function of time, measured by anti-HA blot (upper) and B Coomassie. [m-tyrosinase] = 0.15 mg/ml (based upon mass of lyophilized product). M = molecular weight marker. C Quantitation eDHFR-HA cleavage under various conditions (200 μM dihydrofolate; 200 μM trimethoprim (TMP); 2x Sigma protease inhibitor cocktail P8340 [containing: 4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF), pepstatin A, E-64, bestatin hydrochloride, leupeptin hemisulfate, EDTA and aprotinin)]. For the untreated m-tyrosinase sample ~ 7 x the final amount loaded for each time point is shown.