Riboswitch

Riboswitches are RNA elements in the untranslated regions of the mRNA which bind low molecular weight metabolites, and subsequently regulate gene expression.

You can regulate the transcription or translation of the mRNA own. Regulatory proteins are in this case not necessary. With the exception of TPP ( thiamine pyrophosphate ) riboswitches in Arabidopsis thaliana ( thale cress Common ) all previously known riboswitches are found in prokaryotes. More than 2 % of all genes in the bacterium Bacillus subtilis are recognized by riboswitches. The distribution of riboswitches in other bacteria varies greatly.

RNA forms a secondary and tertiary structure, and thus detects metabolites ( for example, guanine, adenine, L-lysine ). The detection of the ligand occurs very precise about the recognition of charges, functional groups and stereochemical properties. In order to recognize them, there are special bags that are formed among others by stacking and loops. When the ligand binds, it comes with almost all riboswitches to a conformational change in the RNA. Thus, the ribosomal binding site (Shine -Dalgarno sequence ) can be hidden in the inside of the RNA molecule, which does not occur at the start of translation. The conformational change may occur to the formation of a hairpin structure so that the transcription is terminated. The glmS riboswitch the regulation of the transcription is carried out by cleavage of the mRNA upon binding of the ligand.