Figure 5.

(A) Effects of wild-type λcI and λcI superactivators on transcription in the presence of the α-σ³⁸ chimera. SF1 cells harboring the indicated plasmids were assayed for β-galactosidase activity. pACYC-derived plasmids encoded λcI (pACλcI), λcISa109 [pACλcI(Sa109)], or λcISa104 [pACλcI(Sa104)]; the pBR322-derived plasmid encoded the α-σ³⁸ chimera (pBRα-σ³⁸). (B) Interaction between σ³⁸ region 4 and the DNA mediates transcriptional activation. SF1 and SF2 cells harboring the indicated plasmids were assayed for β-galactosidase activity. In each panel, the sequence of the additional −35 element from the relevant test promoter is given. The pACYC-derived plasmid encoded no λcI (pACΔcI); pBR322-derived plasmids encoded either the α-σ³⁸ chimera (pBRα-σ³⁸) or wild-type α (pBRα).