Fig 8.
DNA binding activity of selected alanine substitution mutants. For the EMSA experiment (top), an equimolar mixture of nonspecific (Non-Sp, derived from the coding region of pscF) and specific (Sp, derived from the wt PexsC reporter) radiolabeled probes (0.05 nM each) was incubated for 15 min at 25°C in the absence (−) or presence of 40 nM purified ExsAHis, or 2 μl of whole-cell lysate prepared from E. coli expressing wt ExsA or the indicated alanine substitution mutants. Samples were analyzed by native polyacrylamide gel electrophoresis and phosphorimaging. Anti-ExsA immunoblots (bottom) indicate that the E. coli lysates used in the EMSA experiment contain comparable levels of wt ExsA and the indicated alanine substitution mutants.