Figure 4.

Analysis of enzyme purification by 15% SDS–PAGE; gels are stained with Coomassie brilliant blue. M, marker proteins (Gibco ‘10 kDa protein ladder’ as indicated). Lane 1, crude extract of E.coli cells harboring expression plasmid, before induction. Lane 2, crude extract of cells after induction with IPTG. Lane 3, pooled fractions of Ni²⁺-IMAC (Pharmacia) column (200–300 mM imidazole). Lane 4, pooled fractions of Poros HS cation exchange column (500–600 mM NaCl). (Left) TTUDGA. (Right) TTUDGB.