Ligand-induced folding of the guanine-sensing riboswitch is controlled by a combined predetermined induced fit mechanism.

ABSTRACT: All known guanine-sensing riboswitches regulate gene expression by specifically binding to guanine (G) or related analogs with high affinity to switch off transcription. The aptamers of this class of riboswitches are characterized by three helices (P1-P3), surrounding a central core of phylogenetically conserved nucleotides and a long-range loop-loop interaction. To gain more insight into the switching mechanism, we present here a comparison between the solution-state structures of the G-free and G-bound forms of the guanine aptamer from the xpt-pbuX operon of Bacillus subtilis, as derived from NMR chemical shifts and magnetic-field-induced residual dipolar couplings. The high-resolution NMR analysis shows the G-free aptamer is highly structured with parallel P2 and P3 helices and the long

SUBMITTER: Ottink OM 

PROVIDER: S-EPMC2080608 | biostudies-literature | 2007 Dec

REPOSITORIES: biostudies-literature