title: Structure of the S-adenosylmethionine riboswitch regulatory mRNA element.
abstract: Riboswitches are cis-acting genetic regulatory elements found in the 5'-untranslated regions of messenger RNAs that control gene expression through their ability to bind small molecule metabolites directly. Regulation occurs through the interplay of two domains of the RNA: an aptamer domain that responds to intracellular metabolite concentrations and an expression platform that uses two mutually exclusive secondary structures to direct a decision-making process. In Gram-positive bacteria such as Bacillus species, riboswitches control the expression of more than 2% of all genes through their ability to respond to a diverse set of metabolites including amino acids, nucleobases and protein cofactors. Here we report the 2.9-angstroms resolution crystal structure of an S-adenosylmethionine (SAM)-responsive riboswitch from Thermoanaerobacter tengcongensis complexed with S-adenosylmethionine, an RNA element that controls the expression of several genes involved in sulphur and methionine metabolism. This RNA folds into a complex three-dimensional architecture that recognizes almost every functional group of the ligand through a combination of direct and indirect readout mechanisms. Ligand binding induces the formation of a series of tertiary interactions with one of the helices, serving as a communication link between the aptamer and expression platform domains.
authors.forename: Rebecca K
authors.initials: RK
authors.lastname: Montange
authors.forename: Robert T
authors.initials: RT
authors.lastname: Batey
mesh_terms: D020627:Azoarcus / Q000235:genetics; D001483:Base Sequence; D001665:Binding Sites; D018360:Crystallography, X-Ray; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D007438:Introns / Q000235:genetics; D008024:Ligands; D008715:Methionine / Q000378:metabolism; D008958:Models, Molecular; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012436:S-Adenosylmethionine / Q000737:chemistry / Q000378:metabolism* / Q000494:pharmacology*; D055672:Static Electricity; D013455:Sulfur / Q000378:metabolism; D046968:Thermoanaerobacter / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism
chemical_list: D008024:Ligands; D012329:RNA, Bacterial; D012333:RNA, Messenger; D013455:Sulfur; D012436:S-Adenosylmethionine; D008715:Methionine