Sequence-dependent folding and unfolding of ligand-bound purine riboswitches.
Biopolymers
; 91(11): 953-65, 2009 Nov.
Article
em En
| MEDLINE
| ID: mdl-19603494
ABSTRACT
Riboswitch regulation of gene expression requires ligand-mediated RNA folding. From the fluorescence lifetime distribution of bound 2-aminopurine ligand, we resolve three RNA conformers (C(o), C(i), C(c)) of the liganded G- and A-sensing riboswitches from Bacillus subtilis. The ligand binding affinities, and sensitivity to Mg(2+), together with results from mutagenesis, suggest that C(o) and C(i) are partially unfolded species compromised in key loop-loop interactions present in the fully folded C(c). These data verify that the ligand-bound riboswitches may dynamically fold and unfold in solution, and reveal differences in the distribution of folded states between two structurally homologous purine riboswitches Ligand-mediated folding of the G-sensing riboswitch is more effective, less dependent on Mg(2+), and less debilitated by mutation, than the A-sensing riboswitch, which remains more unfolded in its liganded state. We propose that these sequence-dependent RNA dynamics, which adjust the balance of ligand-mediated folding and unfolding, enable different degrees of kinetic discrimination in ligand binding, and fine-tuning of gene regulatory mechanisms.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Purinas
/
RNA Bacteriano
/
RNA Mensageiro
/
Ligantes
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Conformação de Ácido Nucleico
Idioma:
En
Ano de publicação:
2009
Tipo de documento:
Article