Dataset Information

CCR5 RNA Pseudoknots: Residue and Site-Specific Labeling correlate Internal Motions with microRNA Binding.

ABSTRACT: Conformational dynamics of RNA molecules play a critical role in governing their biological functions. Measurements of RNA dynamic behavior sheds important light on sites that interact with their binding partners or cellular stimulators. However, such measurements using solution-state NMR are difficult for large RNA molecules (>70?nt; nt=nucleotides) owing to severe spectral overlap, homonuclear 13 C scalar couplings, and line broadening. Herein, a strategic combination of solid-phase synthesis, site-specific isotopic labeled phosphoramidites, and enzymatic ligation is introduced. This approach allowed the position-specific insertion of isotopic probes into a 96?nt CCR5 RNA fragment. Accurate measurements of functional dynamics using the Carr-Purcell-Meiboom-Gill (CPMG) relaxation dispersion (RD) experiments enabled extraction of the exchange rates and populations of this RNA. NMR chemical shift perturbation analysis of the RNA/microRNA-1224 complex indicated that A90-C1' of the pseudoknot exhibits similar changes in chemical shift observed in the excited state. This work demonstrates the general applicability of a NMR-labeling strategy to probe functional RNA structural dynamics.

SUBMITTER: Chen B

PROVIDER: S-EPMC7640883 | biostudies-literature | 2018 Apr

REPOSITORIES: biostudies-literature

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Publications

CCR5 RNA Pseudoknots: Residue and Site-Specific Labeling correlate Internal Motions with microRNA Binding.

Chen Bin B Longhini Andrew P AP Nußbaumer Felix F Kreutz Christoph C Dinman Jonathan D JD Dayie T Kwaku TK

Chemistry (Weinheim an der Bergstrasse, Germany) 20180325 21

Conformational dynamics of RNA molecules play a critical role in governing their biological functions. Measurements of RNA dynamic behavior sheds important light on sites that interact with their binding partners or cellular stimulators. However, such measurements using solution-state NMR are difficult for large RNA molecules (>70 nt; nt=nucleotides) owing to severe spectral overlap, homonuclear <sup>13</sup> C scalar couplings, and line broadening. Herein, a strategic combination of solid-phase ...[more]

PMID: 29412477

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Project description:Pentameric ligand-gated ion channels (pLGICs) are neurotransmitter-activated receptors that mediate fast synaptic transmission. In pLGICs, binding of agonist to the extracellular domain triggers a structural rearrangement that leads to the opening of an ion-conducting pore in the transmembrane domain and, in the continued presence of neurotransmitter, the channels desensitize (close). The flexible loops in each subunit that connect the extracellular binding domain (loops 2, 7, and 9) to the transmembrane channel domain (M2-M3 loop) are essential for coupling ligand binding to channel gating. Comparing the crystal structures of two bacterial pLGIC homologues, ELIC and the proton-activated GLIC, suggests channel gating is associated with rearrangements in these loops, but whether these motions accurately predict the motions in functional lipid-embedded pLGICs is unknown. Here, using site-directed spin labeling (SDSL) electron paramagnetic resonance (EPR) spectroscopy and functional GLIC channels reconstituted into liposomes, we examined if, and how far, the loops at the ECD/TMD gating interface move during proton-dependent gating transitions from the resting to desensitized state. Loop 9 moves ∼9 Å inward toward the channel lumen in response to proton-induced desensitization. Loop 9 motions were not observed when GLIC was in detergent micelles, suggesting detergent solubilization traps the protein in a nonactivatable state and lipids are required for functional gating transitions. Proton-induced desensitization immobilizes loop 2 with little change in position. Proton-induced motion of the M2-M3 loop was not observed, suggesting its conformation is nearly identical in closed and desensitized states. Our experimentally derived distance measurements of spin-labeled GLIC suggest ELIC is not a good model for the functional resting state of GLIC, and that the crystal structure of GLIC does not correspond to a desensitized state. These findings advance our understanding of the molecular mechanisms underlying pLGIC gating.

Project description:MotivationThe function of an RNA molecule is not only linked to its native structure, which is usually taken to be the ground state of its folding landscape, but also in many cases crucially depends on the details of the folding pathways such as stable folding intermediates or the timing of the folding process itself. To model and understand these processes, it is necessary to go beyond ground state structures. The study of rugged RNA folding landscapes holds the key to answer these questions. Efficient coarse-graining methods are required to reduce the intractably vast energy landscapes into condensed representations such as barrier trees or basin hopping graphs : BHG) that convey an approximate but comprehensive picture of the folding kinetics. So far, exact and heuristic coarse-graining methods have been mostly restricted to the pseudoknot-free secondary structures. Pseudoknots, which are common motifs and have been repeatedly hypothesized to play an important role in guiding folding trajectories, were usually excluded.ResultsWe generalize the BHG framework to include pseudoknotted RNA structures and systematically study the differences in predicted folding behavior depending on whether pseudoknotted structures are allowed to occur as folding intermediates or not. We observe that RNAs with pseudoknotted ground state structures tend to have more pseudoknotted folding intermediates than RNAs with pseudoknot-free ground state structures. The occurrence and influence of pseudoknotted intermediates on the folding pathway, however, appear to depend very strongly on the individual RNAs so that no general rule can be inferred.Availability and implementationThe algorithms described here are implemented in C++ as standalone programs. Its source code and Supplemental material can be freely downloaded from http://www.tbi.univie.ac.at/bhg.html.Contactqin@bioinf.uni-leipzig.deSupplementary informationSupplementary data are available at Bioinformatics online.

Dataset Information

CCR5 RNA Pseudoknots: Residue and Site-Specific Labeling correlate Internal Motions with microRNA Binding.

Publications

CCR5 RNA Pseudoknots: Residue and Site-Specific Labeling correlate Internal Motions with microRNA Binding.

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