Seeing the invisible – RNA excited state structures

Seeing the invisible using NMR. The research aims at the elucidation of three-dimensional structures of low populated states of RNA. Biomolecules are inherently flexible and these dynamic phenomena are directly linked to their biological function. Within this proposal we plan to expand the existing powerful protein NMR methods and isotope labelling protocols to nucleic acids with the ultimate goal to elucidate high-energy structures with unprecedented precision. For that purpose organic chemistry and NMR spectroscopy will be combined in a unique way to obtain high-resolution structures of weakly populated RNA conformational states, which cannot be studied by other biophysical methods. The anticipated results of the project will have a significant impact on how RNA structure and function will be addressed in future. Bringing into focus the high-resolution structure of low populated RNA conformational states will give new insights how RNAs function in ligand binding and catalysis is encoded in this state.

During the research project significant progress could be made to develop methods that allow the high resolution structural characterization of "invisible" states in nucleic acids. By using a combination of nuclear magnetic resonance (NMR) and computational methods, insights into the high resolution structure of so called excited states could be obtained. These excited states are populated only to a small degree, but are often very important for the function of the respective nucleic acid. In the research project the transient low populated structure of the ribosomal A-site RNA was investigated. This RNA is crucial for the ribosome function and the excited state structure was found to impair the correct ribosome function. This was also confirmed by a biological experiment. The now developed methods are now generally applicable to nucleic acids and will allow to describe low populated structures at high resolution. This is of special interest for RNAs occurring in pathological species, such as bacteria and viruses. The invisible states of such viral and bacterial RNAs can now be fully characterized. Thereby, drug targeting these low populated but functional states is facilitated.