Abstract
Conformational changes are essential for protein-protein and protein-ligand recognition. Here we probed changes in the structure of the protein ubiquitin at low temperatures in supercooled water using NMR spectroscopy. We demonstrate that ubiquitin is well folded down to 263 K, although slight rearrangements in the hydrophobic core occur. However, amide proton chemical shifts show non-linear temperature dependence in supercooled solution and backbone hydrogen bonds become weaker in the region that is most prone to cold-denaturation. Our data suggest that the weakening of the hydrogen bonds in the β-sheet of ubiquitin might be one of the first events that occur during cold-denaturation of ubiquitin. Interestingly, the same region is strongly involved in ubiquitin-protein complexes suggesting that this part of ubiquitin more easily adjusts to conformational changes required for complex formation.
Highlights
Conformational changes are essential for protein-protein and protein-ligand recognition [1]
We investigated the structure of the 76residue protein ubiquitin at low temperatures in supercooled water using NMR spectroscopy
For several other residues the chemical shift changes deviated from a linear temperature dependence (Figure S1)
Summary
Conformational changes are essential for protein-protein and protein-ligand recognition [1]. Many residues such as Q62 displayed linearly changing chemical shifts across the whole temperature range (Figure 1B–E and Figure S1), as expected for stably folded structures and in agreement with the known hydrogen bonds of ubiquitin [17,18].
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