Expression of the BmOVO zinc-finger domain in Escherichia coli

The sequence encoding the last 178 aa containing the four zinc-finger domains of BmOVO was amplified with the primer pairs Bmovo2–3/Bmovo2–2 (Additional file 1: Table S3) and was then cloned into the pET28a (+) vector (Invitrogen) for the expression of the recombinant BmOVO zinc-finger domain in E. coli. The recombinant protein BmOVO zinc-finger domain with 6-His-tagged was purified with Ni-NTA agarose (Jinyitai, Wuhan, China) according to the manufacturer’s instructions. Then, the refolding of the BmOVO zinc-finger domain was carried out by dialysis in TGN buffer (50 mM Tris-base, 0.5 mM EDTA, 50 mM NaCl, 1% arginine, 10% glycerol, 5 mM GSSG and 2 mM DTT).