User:Emilie.secherre/sandbox

This family is a riboswitch generally regulating a BglG transcriptional antiterminator. But it can also regulate LicT transcriptional antiterminators or a PTS sugar transporter. The RNA has a sequence approximately 129 nucleotides in length. Its secondary structures include four stem-loops, one particularly taller than the others. This cis-regulator is present at the 5′ UTR ends of each of the regulated genes. The antitermination mechanism plays a pivotal role in the regulation of PTS β-glucoside genes in many bacteria. Gene regulation has been well studied in Escherichia coli and Bacillus subtilis. In the antitermination regulatory mechanism, transcription stops at a terminator sequence present in the 5' untranslated region (UTR) of the target mRNA. In the presence of sugar, a transcriptional antiterminator protein of the BglG/SacY family binds to the ribonucleic antiterminator sequence (RAT) partially overlapping the transcriptional terminator and thus causes an increase of transcription at the end of the target gene. An antiterminator such as BglG, in E.coli, or LicT, in B.subtilis, is inactivated by phosphorylation in the regulatory domain PTS 1 (PRD-1) by a β-glucoside while it is activated by the dephosphorylation of PRD-1, resulting in upregulation of the PTS gene of β-glucoside. The rapid glucose metabolism is responsible for the strict suppression of the expression of β-glucoside-PTS. This repression by glucose, which is important for the preferential use of glucose, is generally observed in the regulation of carbohydrate metabolism in bacteria. Thus, the cis-regulator makes it possible to regulate the expression of β-glucosides, especially in firmicutes, either by regulating the antitermination genes involved in the metabolism of β-glucosides (BglG or LicT) or else by regulating the concentration sugar from the bacteria which is also an actor in the expression of β-glucosides.