S. Ryu et al., EFFECT OF THE FRUR REGULATOR ON TRANSCRIPTION OF THE PTS OPERON IN ESCHERICHIA-COLI, The Journal of biological chemistry, 270(6), 1995, pp. 2489-2496
The promoters of the pts operon of Escherichia coil are controlled by
the cyclic AMP receptor protein (CRP) complexed with cAMP (CRP.cAMP).
In addition, glucose stimulates pts operon expression in vivo. The pts
promoter region has a fructose repressor (FruR)-binding site (the Fru
R box) that partially overlaps with one of the CRP.cAMP-binding sites.
The effects of the pleiotropic transcriptional regulator FruR on pfs
operon expression were studied to determine whether the in vivo glucos
e effect on pts operon expression is mediated by FruR. In vitro, FruR
can repress P1b transcription, which is activated by CRP.cAMP, and res
tore P1a transcription, which is repressed by CRP.cAMP. FruR can displ
ace CRP cAMP from its binding site in the presence of RNA polymerase e
ven though FruR and CRP.cAMP can bind simultaneously to their partiall
y overlapping binding sites in the absence of RNA polymerase. FruR had
very little effect on the transcription of the P0 promoter, which is
most important for regulation by glucose. Consistent with the in vitro
results, pts P0 transcription did not increase as much In cells grown
in the presence of fructose or in fruR(-) mutant cells as in cells gr
own in the presence of glucose. These results suggest that FruR alone
does not mediate the in vivo glucose effect on pts operon expression.