SDS-PAGE analysis of protein fractions containing the recombinant cE5 after the different purification steps. M, Prosieve QuadColor Protein Marker, 4.6–300 kDa (Lonza, Cologne, GmbH). (a) Expression levels of the MBP-cE5 fusion protein after induction. I, induced; NI, non induced. (b) Purification of MBP-cE5 by Ion-Exchange Chromatography (IEC). (c) Recombinant MBP-cE5 after Affinity Chromatography (AC). (d) Final purification by TEV cleavage (TC) and RP-HPLC (LC).