Fig. 3

E. coli expression system using BL21-pSUMO-artilysin engineered bacteria for protein production and purification. a The growth curve for BL21-pSUMO-artilysin at 37 ℃. b Fermentation map following high-density fermentation in a 5-l fermenter. c SDS-PAGE gel of BL21-pSUMO-artilysin before and after the addition of isopropyl β-d-1-thiogalactopyranoside. 1: Marker; 2: BL21-pSUMO-artilysin1 bacteria before induction; 3: BL21-pSUMO-artilysin1 bacteria after induction; 4: BL21-pSUMO-artilysin2 bacteria before induction; 5: BL21-pSUMO-artilysin2 bacteria after induction. d SDS-PAGE gels (1 and 3) of the collected eluates. The later peak contains fewer impurities, and the target protein purity is greater. (1) 1: Marker; 2: Precipitate after lysis of BL21-pSUMO-artilysin1 bacteria; 3: Supernatant after lysis of BL21-pSUMO-artilysin1 bacteria; 4: Blank; 5: Flowthrough; 6: Postpeak of elution; 7: Middle peak of elution; 8: Prepeak of elution; 9: Alkaline wash. (3) 1: Marker; 2: Precipitate after lysis of BL21-pSUMO-artilysin2 bacteria; 3: Supernatant after lysis of BL21-pSUMO-artilysin2 bacteria; 4: Flowthrough; 5: Prepeak of elution; 6: Middle peak of elution-1; 7: Middle peak of elution-2; 8: Middle peak of elution-3; 9: Postpeak of elution; 10: Alkaline wash. SUMO enzyme was used to digest the EP-LP, thus producing artilysins. SDS-PAGE protein gels (2 and 4) showing artilysins after preliminary purification. (2) 1: Marker; 2: SUMO-artilysin1; 3: artilysin 1. (4) 1: Marker; 2: SUMO-artilysin2; 3: artilysin 2