2.1 AraC protein purification
AraC was overproduced by the pET24 expression vector (Novagen) and purified by sequential heparin and HiTrap-Q ion exchange columns, as previously described.18 The protein stock solution contained 93 µM full-length AraC, 20 mM Na3PO4, 5 mM arabinose, 0.1 mM NaN3, and 500 mM NaCl, pH 6.5.