Fig. 1.
Activation of BglG requires intact HPr that can be phosphorylated and this requirement can partially be complemented by FruB. Strains were tested that carried deletions of the bgl and lac operons (WT) and additional deletions as indicated at Left. All strains also carried an artificial bglG–bglF operon under control of the IPTG-inducible Ptac promoter ectopically integrated into the λattB site on the chromosome (Upper Right). Strains were cotransformed with plasmid pFDX3158 as reporter for BglG antitermination activity (Upper Left) and an additional plasmid carrying the genes as indicated under Ptac control. Bacteria were grown in M9 glycerol medium. IPTG (1 mM) for induction of Ptac-controlled genes and salicin (7 mM) as substrate for BglF were added as indicated. β-Galactosidase activities were determined from exponentially grown cells. The following strains carrying plasmid pFDX3158, and in addition the plasmids given in parentheses, were used: Bars 1, R1752; bars 2, R2013; bars 3, R2013 (pFDX3851); bars 4, R2013 (pFDX3852); bars 5, R2013 (pFDX3161); bars 6, R1977; bars 7, R1977 (pFDX3851); bars 8, R1977 (pFDX3852); bars 9, R1977 (pFDX3161); bars 10, R1977 (pFDX3221); bars 11, R1977 (pFDX4732); and bars 12, R1977 (pFDX3214).