ykkC riboswitches employ an add-on helix to adjust specificity for polyanionic ligands.
Nat Chem Biol
; 14(9): 887-894, 2018 09.
Article
em En
| MEDLINE
| ID: mdl-30120360
ABSTRACT
The ykkC family of bacterial riboswitches combines several widespread classes that have similar secondary structures and consensus motifs but control different genes in response to different cellular metabolites. Here we report the crystal structures of two distinct ykkC riboswitches specifically bound to their cognate ligand ppGpp, a second messenger involved in stress response, or PRPP, a precursor in purine biosynthesis. Both RNAs adopt similar structures and contain a conserved core previously observed in the guanidine-specific ykkC riboswitch. However, ppGpp and PRPP riboswitches uniquely employ an additional helical element that joins the ends of the ligand-sensing domains and creates a tunnel for direct and Mg2+-mediated binding of ligands. Mutational and footprinting experiments highlight the importance of conserved nucleotides forming the tunnel and long-distance contacts for ligand binding and genetic response. Our work provides new insights into the specificity of riboswitches and gives a unique opportunity for future studies of RNA evolution.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Polímeros
/
Riboswitch
Idioma:
En
Ano de publicação:
2018
Tipo de documento:
Article