Fig 2. Expression and purification of CPD.

(A) Schematic diagram of the strategy for expression and purification of rhCPD and mutants. Protein expression was performed by transient transfection of suspension-growing HEK293F cells. Extracellular medium was collected after 7 days incubation, followed by purification of the recombinant proteins in three steps; (1) hydrophobic interaction chromatography using a Butyl 650-M, (2) affinity chromatography using anti-Strep-tag resin, and (3) gel filtration chromatography. (B) Coomassie-stained SDS–PAGE showing the purity of recombinant CPD proteins.