Riboswitch

Secondary structure of a purine riboswitch from Bacillus subtilis

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

You can regulate the transcription or translation of your own mRNA. In this case, regulator proteins are not necessary. Most riboswitches are found in prokaryotes . Nevertheless, they also occur in archebacteria , fungi and plants ( thiamine pyrophosphate riboswitches in Arabidopsis thaliana ). More than two percent of all genes in the Bacillus subtilis bacterium are recognized by riboswitches. The distribution of riboswitches in other bacteria varies greatly.

The RNA forms a secondary and tertiary structure and thus recognizes metabolites ( e.g. guanine , adenine , L-lysine ). This structure is mostly an aptamer . The ligands are recognized very precisely via the recognition of charges, functional groups and stereochemical properties. In order to recognize these there are special pockets that are formed by stacking and grinding, among other things . When the ligand binds, a conformational change in the RNA occurs in almost all riboswitches. This allows the ribosomal binding site ( Shine-Dalgarno sequence ) to be hidden inside the RNA molecule, preventing translation from starting . The change in conformation can also lead to the formation of a hairpin structure , whereby the transcription is interrupted. In the GlmS riboswitch, transcription is regulated by cleaving the mRNA after binding the ligand. The length of riboswitches varies between 35 and 200 bp.

literature

WC Winkler, A. Nahvi et al. a .: Control of gene expression by a natural metabolite-responsive ribozyme. In: Nature. Volume 428, Number 6980, March 2004, pp. 281-286, ISSN 1476-4687 . doi : 10.1038 / nature02362 , PMID 15029187 .
Sashital, DG & Butcher, SE (2006): Flipping off the riboswitch: RNA structures that control gene expression. In: ACS Chem. Biol. Vol. 1, pp. 341-345, PMID 17163768 doi : 10.1021 / cb6002465 .

Individual evidence

↑ Jeremy Grojean, Brian Downes: Riboswitches as hormone receptors: hypothetical cytokinin-binding riboswitches in Arabidopsis thaliana . In: Biology Direct . tape 5 , no. 1 , 2010, ISSN 1745-6150 , p. 60 , doi : 10.1186 / 1745-6150-5-60 .
^ Antonio Blanco, Gustavo Blanco: Regulation of Gene Expression . In: Medical Biochemistry . Elsevier, 2017, ISBN 978-0-12-803550-4 , pp. 525-533 , doi : 10.1016 / b978-0-12-803550-4.00023-9 ( elsevier.com [accessed October 23, 2019]).

[1] Jeremy Grojean, Brian Downes: Riboswitches as hormone receptors: hypothetical cytokinin-binding riboswitches in Arabidopsis thaliana . In: Biology Direct . tape 5 , no. 1 , 2010, ISSN 1745-6150 , p. 60 , doi : 10.1186 / 1745-6150-5-60 .

[2] Antonio Blanco, Gustavo Blanco: Regulation of Gene Expression . In: Medical Biochemistry . Elsevier, 2017, ISBN 978-0-12-803550-4 , pp. 525-533 , doi : 10.1016 / b978-0-12-803550-4.00023-9 ( elsevier.com [accessed October 23, 2019]).