Plasmids pWKS1245 and pWKS1251 were transformed into E. coli Rosetta(DE3) pLysS (Novagen). Transformants were used to inoculate 25 mL of LB with appropriate antibiotics. After overnight incubation, the cells were 1:100 diluted in 500 mL fresh medium containing appropriate antibiotics. Protein production was induced with 1 mM IPTG at an OD600 of 0.7 and growth was continued for another three hours before harvesting. Cells were washed with ice cold PBS and stored at 280uC for later use. Purification of the proteins was essentially done as described [10] . In short, cells were disrupted in 4 mL lysis buffer (2 mM PMSF, 10 mM imidazole, 5 mM beta-mercaptoethanol, 300 mM NaCl, 50 mM NaH 2 PO 4 , pH 7.9). Cleared cell lysates we incubated with 2 mL pre-equilibrated 50% TALON slurry (Clontech) in a final volume of 15 mL lysis buffer for 1 hr. The resin was allowed to settle on a Poly-Prep column (BioRad) and washed with 2 mL wash buffer (20 mM imidazole, 300 mM NaCl, 50 mM NaH 2 PO 4 , pH 7.9). The protein was stepwise eluted in 1 mL fractions after applying 2 mL elution buffer to the column (identical to wash buffer but with 50, 100, 250 or 500 mM imidazole). The whole procedure was carried out at 4uC. Fractions were assayed for purity and yield and suitable fractions were dialysed against 26 1L dialysis buffer (50 mM Tris-HCl pH 8, 1 mM EDTA, 0.5 mM DTT) using Slide-A-Lyzer cassettes with a molecular weight cut-off of 3.5 kDa (Pierce).