Structural Transitions and Thermodynamics of a Glycine-Dependent Riboswitch from Vibrio cholerae
2007
Riboswitches are complex folded RNA domains found in noncoding regions of mRNA that regulate gene expression upon small molecule binding. Recently, Breaker and coworkers reported a tandem aptamer riboswitch (VCI-II) that binds glycine cooperatively. Here, we use hydroxyl radical footprinting and small-angle X-ray scattering (SAXS) to study the conformations of this tandem aptamer as a function of Mg 2+ and glycine concentration. We fit a simple three-state thermodynamic model that describes the energetic coupling between magnesium-induced folding and glycine binding. Furthermore, we characterize the structural conformations of each of the three states: In low salt with no magnesium present, the VCI-II construct has an extended overall conformation, presumably representing unfolded structures. Addition of millimolar concentrations of Mg 2+ in the absence of glycine leads to a significant compaction and partial folding as judged by hydroxyl radical protections. In the presence of millimolar Mg 2+ concentrations, the tandem aptamer binds glycine cooperatively. The glycine binding transition involves a further compaction, additional tertiary packing interactions and further uptake of magnesium ions relative
Keywords:
- Correction
- Source
- Cite
- Save
- Machine Reading By IdeaReader
80
References
109
Citations
NaN
KQI