Figure 3.

Analysis of the purified ompA mRNA-binding protein RBA. (A) Electrophoresis of crude and purified materials on an SDS-polyacrylamide gel visualized by silver staining. Purification steps of RBA described in Materials and Methods. Lane 1, crude extract (10 μg); lane 2, heparin-agarose fraction (0.1 μg); lane 3, finely purified material (Hfq) (0.005 μg). (B) Mobility-shift assay of crude cell extract and purified material as in A, using as an RNA substrate either ompA or lpp. The same amounts of protein as in A were incubated with ³²P-labeled substrates and applied to the 4% native polyacrylamide gel.