The structure of the SAM/SAH-binding riboswitch.
Nucleic Acids Res
; 47(5): 2654-2665, 2019 03 18.
Article
em En
| MEDLINE
| ID: mdl-30590743
ABSTRACT
S-adenosylmethionine (SAM) is a central metabolite since it is used as a methyl group donor in many different biochemical reactions. Many bacteria control intracellular SAM concentrations using riboswitch-based mechanisms. A number of structurally different riboswitch families specifically bind to SAM and mainly regulate the transcription or the translation of SAM-biosynthetic enzymes. In addition, a highly specific riboswitch class recognizes S-adenosylhomocysteine (SAH)-the product of SAM-dependent methyl group transfer reactions-and regulates enzymes responsible for SAH hydrolysis. High-resolution structures are available for many of these riboswitch classes and illustrate how they discriminate between the two structurally similar ligands SAM and SAH. The so-called SAM/SAH riboswitch class binds both ligands with similar affinities and is structurally not yet characterized. Here, we present a high-resolution nuclear magnetic resonance structure of a member of the SAM/SAH-riboswitch class in complex with SAH. Ligand binding induces pseudoknot formation and sequestration of the ribosome binding site. Thus, the SAM/SAH-riboswitches are translational 'OFF'-switches. Our results establish a structural basis for the unusual bispecificity of this riboswitch class. In conjunction with genomic data our structure suggests that the SAM/SAH-riboswitches might be an evolutionary late invention and not a remnant of a primordial RNA-world as suggested for other riboswitches.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
S-Adenosil-Homocisteína
/
S-Adenosilmetionina
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Biossíntese de Proteínas
/
Riboswitch
Idioma:
En
Ano de publicação:
2019
Tipo de documento:
Article