FIG. 4.

Copurification of PvdS with the core fraction of E. coli RNAP. The FLAG-tagged PvdS protein (PvdSF) was overexpressed in E. coli M15(pDMI,1) carrying the pPvdSF expression plasmid and purified under nondenaturing conditions from the soluble cell fraction. Lane 1, whole cell extracts of the uninduced culture; lane 2, whole cell extracts of the induced culture; lane 3, PvdS-RNAP complex (subunits α₂ββ′), eluted from the FLAG affinity column; lane 4, commercial vegetative RNAP (subunits ς⁷⁰α₂ββ′; Epicentre Technologies). Protein size markers (high and medium range; Bio-Rad) are shown on the left. (A) SDS-PAGE analysis of protein samples. (B) Western blot analysis with anti-FLAG antibodies. (C) Western blot analysis with antibodies against the α subunit of the E. coli RNAP.