Overexpression was induced by adding 80 µL of 500 mM isopropyl β-D-1thiogalactopyranoside solution. The culture was incubated over night at 20 °C with constant shaking (225 rpm). Growth was stopped by centrifugation (4.000 x g) and the cell pellet was resuspended in lysis buffer (50 mM sodium phosphate, 300 mM sodium chloride, pH 8.0). Bacterial cells were lysed by sonication (pulse 3 x 20 s, amplitude 50 %, pause 59,9 s) using a Sonifier W-250 D (Branson Ultrasonics, USA) and the lysate was centrifuged at 4 °C and 14.000 x g for 30 min. The supernatant was then used for immobilized metal affinity chromatography to purify the overexpressed proteins.