Figure 2. Isolation of a TorA–TorD^His and TorA_ΔSP–TorD^His complex.

(A and C) TorD^His-containing fractions after metal chelate chromatography of cell extracts overproducing (A) TorA and TorD^His or (C) TorA_ΔSP and TorD^His were pooled, concentrated and applied to a HiLoad 16/60 Superdex 200 Prep Grade size-exclusion column. Eluted protein was monitored by measuring absorbance at 280 nm. The column was calibrated with the standard proteins ribonuclease (14 kDa), carbonic anhydrase (29 kDa), ovalbumin (44 kDa), conalbumin (75 kDa), aldolase (158 kDa) and ferritin (440 kDa), and the linear regression analysis is shown as inset boxes. R²=0.9976, y=−23.5x+126.83. MW, molecular mass. (B and D) SDS/PAGE analysis (12% gels) of (B) the concentrated fractions after metal chelate chromatography (Ni pool), and the non-concentrated and concentrated peak fractions from SEC of the TorA–TorD^His complex and (D) the concentrated peak fraction from SEC of the TorA_ΔSP–TorD^His complex. Molecular masses are indicated in kDa.