Figure 1.

SDS–PAGE gels [12.5%(w/v) acrylamide; coloured by the Coomassie staining technique] showing purification of the holo-His₆-HasA–HasR complex. Lane 1, solubilized membrane fraction in 100 mM Tris–HCl pH 7.5, 2%(w/v) ZW3-14; lane 2, complex of holo-His₆-HasA (21 500 Da) and HasR (94 800 Da) after the first affinity chromatography step (nickel–NTA) in 50 mM Tris–HCl pH 7.5, 0.08%(w/v) ZW3-14; lane 3, holo-His₆-HasA–HasR after the last ion-exchange chromatography step (Q-Sepharose) in 20 mM Tris–HCl pH 7.5, 0.6%(w/v) C₈E₅; lane 4, marker proteins (kDa; BioRad).