Interaction between EcfF and OsrA monitored in a bacterial two-hybrid system.

A. Schematic representation of analyzed hybrid proteins. B. pertussis adenylate cyclase fragments T18 and T25 (oval shaped) were translationaly fused to σ factor EcfF (black rectangle) and anti-σ factor OsrA (grey rectangle; wild-type (wt) or mutant variants), respectively. Plasmids encoding respective proteins were transformed into E. coli BTH101 in the indicated combinations to yield strains 1 to 4. B. E. coli cultures were grown for 18 h at 30°C and assayed for β-galactosidase activity. Control strain 5 containing vectors pKT25 and pUT18C was used to determine background activity. Shown are mean values and standard deviations derived from a representative experiment with four independent cultures per strain.