FIG. 4.

Binding of σ²⁸ and derivatives to core RNAP in Salmonella. (A) Immunoblot showing the results of a coimmunoprecipitation assay from Salmonella fliA mutant TH7034, which expresses σ²⁸ or derivatives as indicated above each lane. A strain expressing E. coli σ²⁸, which is identical to Salmonella σ²⁸, was the negative control. Cell lysates were subjected to immunoprecipitation using anti-β monoclonal antibody as described in Materials and Methods. Precipitated proteins were separated by PAGE and immunoblotted with anti-σ²⁸ antibody or anti-β monoclonal antibody. (B) Relative binding affinity of σ²⁸ or derivatives for core. The amount of precipitated σ²⁸ protein is reported as a percentage of the level of β in core RNAP.