URANUS project

Ultrahigh resolution and anisotropic NMR to unravel conformational ensembles of flexible biopolymers: A general strategy

Understanding the function of flexible biopolymers such as disordered proteins, glycans or oligonucleotides requires insight in their conformational ensembles. Liquid-state NMR is the leading technique reporting on this. Unfortunately, fast structural averaging on the NMR time scale strongly reduces chemical shift dispersion, which, given the many 1H-1H couplings, results in spectral overlap. This obstructs resolving 1H NMR data, such as residual dipolar couplings (RDCs), that report on long-range structural order and allosteric changes. In addition, molecular flexibility has until now greatly complicated the interpretation of RDC data. URANUS proposes a general strategy to solve both these issues for any biopolymer. First, it capitalizes on recent ‘pure shift’ methods to boost spectral resolution and RDC extraction by an order of magnitude. Second, a recently introduced method is used to treat RDC data in presence of molecular flexibility: Molecular Dynamics simulations with Orientational Constraints (MDOC). Both these approaches have recently been introduced for small molecule NMR, and in this project their use will be explored for the first time for conformational ensemble analysis of biopolymers. This approach will be directly applied to two biomedically relevant case-studies where insight in the conformational ensemble is key to comprehend the relation between molecular structure and biological activity. (1) The proline-rich region of the non-structural protein 5A (NS5A), a disordered protein region where it has been shown that transient conformations that are yet unidentified play an essential role in Hepatitis C virus RNA replication. (2) Oligosaccharides fragments of the structurally heterogeneous and flexible polysaccharide heparin, which is a clinically very important anticoagulant whose activity is determined by specific sulfation patterns, but conformational ensemble as a function of these patterns is not yet fully understood.

URANUS aims to take the determination of conformational ensembles to a next level by maximizing the amount of spectral information and facilitating their translation into the ensemble. The goal is to provide a better description of conformational ensembles than currently feasible, allowing to resolve the subtleties necessary to clearly link biopolymers molecular structure to biological activity. On the mid-term, we will create a widely accessible toolbox of techniques that is generally applicable to any biopolymer.

⏐ From January, 2021 ⏐ https://anr.fr/Project-ANR-20-CE29-0015