Conformational dynamics of asparagine at coiled-coil interfaces
journal contributionposted on 15.10.2020, 08:54 by Franziska Thomas, Ai Niitsu, Alain Oregioni, Gail J Bartlett, Derek N Woolfson
Coiled coils (CCs) are among the best-understood protein folds. Nonetheless, there are gaps in our knowledge of CCs. Notably, CCs are likely to be structurally more dynamic than often considered. Here, we explore this in an abundant class of CCs, parallel dimers, focusing on polar asparagine (Asn) residues in the hydrophobic interface. It is well documented that such inclusions discriminate between different CC oligomers, which has been rationalized in terms of whether the Asn can make side-chain hydrogen bonds. Analysis of parallel CC dimers in the Protein Data Bank reveals a variety of Asn side-chain conformations, but not all of these make the expected inter-side-chain hydrogen bond. We probe the structure and dynamics of a de novo-designed coiled-coil homodimer, CC-Di, by multidimensional nuclear magnetic resonance spectroscopy, including model-free dynamical analysis and relaxation-dispersion experiments. We find dynamic exchange on the millisecond time scale between Asn conformers with the side chains pointing into and out of the core. We perform molecular dynamics simulations that are consistent with this, revealing that the side chains are highly dynamic, exchanging between hydrogen-bonded-paired conformations in picoseconds to nanoseconds. Combined, our data present a more dynamic view for Asn at CC interfaces. Although inter-side-chain hydrogen bonding states are the most abundant, Asn is not always buried or engaged in such interactions. Because interfacial Asn residues are key design features for modulating CC stability and recognition, these further insights into how they are accommodated within CC structures will aid their predictive modeling, engineering, and design.
Amino Acid SequenceAsparagineComputer SimulationDatabases, ProteinDimerizationHydrogen BondingHydrophobic and Hydrophilic InteractionsMagnetic Resonance SpectroscopyMolecular Dynamics SimulationProtein ConformationProtein Structure, SecondaryProteinsNMRBiochemistry & Molecular Biology0601 Biochemistry and Cell Biology1101 Medical Biochemistry and Metabolomics0304 Medicinal and Biomolecular Chemistry