RRM
2010 Rustbelt RNA Meeting
RRM
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Talk abstracts
Abstract:
Cyclic diguanylate (c-di-GMP) is a second messenger signaling molecule important for the regulation of many bacterial processes, including virulence, motility, and biofilm formation. Recent developments have shown that c-di-GMP is recognized by a riboswitch, an mRNA domain that controls gene expression in response to varying concentrations of a target ligand. The c-di-GMP riboswitch has been shown to undergo a global structural rearrangement in response to ligand binding. We have used single molecule fluorescence resonance energy transfer (smFRET) to investigate this conformational change. In the absence of c-di-GMP, the riboswitch exists in primarily an undocked conformation and only in the presence of the correct substrate can it fold into a stable docked conformation. This docked conformation was found to be stable for at least 30 minutes. As this riboswitch is responsible for the regulation of many critical bacterial processes, the stability of the docked conformation in the presence of c-di-GMP may be important to ensure a constant expression of required genes. In the presence of c-di-AMP, the riboswitch displayed conformational behavior similar to that in the absence of substrate, demonstrating the specificity of this riboswitch. A population of dynamic molecules that exists primarily in a folded conformation was found to increase in the presence of high magnesium concentrations leading to the idea that magnesium ions aid in the conformational switch from an undocked to folded conformation but are not able to fully stabilize the docked conformation.
Keywords: single molecule FRET, riboswitch, c-di-GMP
