Riboswitch: Difference between revisions
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Normally, a variety of proteins and protein cofactors control gene expression in an organism by binding to different sites on messenger RNA (mRNA). '''Riboswitches''' are genetic regulatory elements that are built directly into the RNA. They are a type of noncoding RNA that regulate gene expression in the absence of proteins by switching from one structural conformation (shape) to another in response to ligand binding | Normally, a variety of proteins and protein cofactors control gene expression in an organism by binding to different sites on messenger RNA (mRNA). '''Riboswitches''' are genetic regulatory elements that are built directly into the RNA. They are a type of noncoding RNA that regulate gene expression in the absence of proteins by switching from one structural conformation (shape) to another in response to ligand binding. Most contain a single binding site that recognizes a specific ligand. The ability of a riboswitch to discriminate against molecules that are similar or closely related to its ligand is essential to prevent metabolic misregulation<ref name=scimag>Breaker, Ronald R. (28 March, 2008). Complex Riboswitches. ''Science'', 319(5871), 1795-1797. doi:[http://dx.doi.org/10.1126/science.1152621 10.1126/science.1152621]</ref>. | ||
The various classes of riboswitches discovered so far are differentiated by their respective ligands. Every class of riboswitch is characterized by an aptamer (binding site) domain, which provides the site for ligand binding, and an expression platform that undergoes conformational change. The sequences and structures of aptamer domains are highly conserved, and therefore exhibit little variation among riboswitches belonging to the same class. | |||
Atomic-resolution structures of riboswitch binding sites show that they make numerous hydrogen bonds with their ligands, forming contacts that stabilize RNA interactions to further increase affinity. Some binding sites form pockets that entirely engulf the ligand, and in these instances an induced-fit mechanism of binding must occur. | Atomic-resolution structures of riboswitch binding sites show that they make numerous hydrogen bonds with their ligands, forming contacts that stabilize RNA interactions to further increase affinity. Some binding sites form pockets that entirely engulf the ligand, and in these instances an induced-fit mechanism of binding must occur. | ||
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[[3gao]] - BsGR + xanthine<br /> | [[3gao]] - BsGR + xanthine<br /> | ||
[[2xnw]] – BsGR + Mn | [[2xnw]] – BsGR + Mn | ||
Thiamine pyrophosphate riboswitch=== | ===Thiamine pyrophosphate riboswitch=== | ||
[[2gd]]i – TPPR + TPP – synthetic<br /> | [[2gd]]i – TPPR + TPP – synthetic<br /> | ||
[[2hoj]], [[2hok]], [[2hol]] – EcTPPR + TPP + metal ion – Escherichia coli<br /> | [[2hoj]], [[2hok]], [[2hol]] – EcTPPR + TPP + metal ion – Escherichia coli<br /> | ||