Rare Conformations in RNA Backbone

At last year’s ACA meeting, we presented a high-quality, residue-filtered dataset of RNA residues. This RNA2023 dataset is useful for defining the most common modes of RNA conformations, and for assembling libraries of expected behaviors. However, structural biology does not depend solely on common behaviors. Rare conformations and their justifications are fascinating and crucial to understanding structure and function. Here we present unusual RNA features gleaned from our high-quality RNA2023 dataset. These include: Previously “wannabe” backbone conformations - some of which are supported by the new data and some of which are not, non-standard ribose sugar puckers such as C1’-exo, and residues with unusual, non-rotameric values for the gamma backbone dihedral. These rare features should be identified, appreciated, and not lost to over-regularization when supported by experimental data.