Purification of recombinant PgD5 produced by E. coli BL21 (Origami pLys S) DE3. (A) RP-HPLC chromatography of the His6-SUMO-PgD5 fusion protein after cleavage with the SUMO protease. Elution times are marked. (B) SDS-PAGE analysis of the His6-SUMO-PgD5 fusion before and after SUMO protease treatment. Lane M, low molecular weight marker (New England Biolabs). Lane 1, Purified fusion protein by Ni-NTA column. Lane 2, SUMO protease cleavage products after 60 min. Lane 3, Purified PgD5 peptide after SUMO protease digestion and reverse-phase chromatography. (C) Mass spectrometric analysis of recombinant PgD5 after separation from the His6-SUMO tag using reverse-phase chromatography.