Fig. 4. σ^S(Δ7–35) binds to phosphorylated RssB in vitro. Equimolar amounts (0.3 nmol) of S-TRX-His₆-RssB and His₆-σ^S or His₆-σ^S(Δ7–35) were incubated at room temperature with or without 50 mM acetyl phosphate (Ac-P), and subject to affinity chromatography on S-protein agarose, separated by SDS–PAGE and visualized using Penta-His antibodies. Size standard proteins (49 and 32.5 kDa) are shown in lane 1. In lanes 2 and 3, His₆-σ^S and His₆-σ^S(Δ7–35), respectively, were directly loaded on the gel.