Cocrystal structure of a class I preQ1 riboswitch reveals a pseudoknot recognizing an essential hypermodified nucleobase.

Publication Type:

Journal Article

Source:

Nature structural & molecular biology, Volume 16, Issue 3, p.343-4 (2009)

Keywords:

2009, Bacillus subtilis, Basic Sciences Division, Crystallography, X-Ray, Models, Molecular, Nucleic Acid Conformation, Nucleoside Q, RNA, Bacterial, RNA, Messenger

Abstract:

Riboswitches are mRNA domains that bind metabolites and modulate gene expression in cis. We report cocrystal structures of a remarkably compact riboswitch (34 nucleotides suffice for ligand recognition) from Bacillus subtilis that is selective for the essential nucleobase preQ(1) (7-aminomethyl-7-deazaguanine). The structures reveal a previously unrecognized pseudoknot fold and suggest a conserved gene-regulatory mechanism whereby ligand binding promotes sequestration of an RNA segment that otherwise assembles into a transcriptional antiterminator.