Then isopropyl b-D-1-thiogalactopyranoside (Sigma-
Aldrich, MO) was added to give a final concentration of 1 mM to
induce protein expression. Cells were harvested by centrifugation
for 20 min at 8000 rpm after 5 h of expression. For large-scale
expression a Bioflo 3000 (New Brunswick Scientific, NJ) fermentor
was used. The pellet was resuspended in denaturing buffer
(100 mM NaH2PO4, 10 mM Tris–HCl, 8 M urea) and stirred overnight
at 4 C.