Evaluating Unexpectedly Short Non-covalent Distances in X-ray Crystal Structures of Proteins with Electronic Structure Analysis
Name
Evaluating_Unexpectedly_Short_Non-covalent_Distances_in_X-ray_Crystal_Structures_of_Proteins_with_Electronic_Structure_A_v1.pdf
Description
Submitted version
Size
10.06 MB
Format
Adobe PDF
Checksum (MD5)
ffcc048faec751949ecd901814a9ffcf
Author(s)
Qi, Helena W.
Kulik, Heather J.
Date Issued
March 2019
Journal
Journal of Chemical Information and Modeling
Publisher
American Chemical Society (ACS)
Citation
Qi, Helena W. and Heather J. Kulik. "Evaluating Unexpectedly Short Non-covalent Distances in X-ray Crystal Structures of Proteins with Electronic Structure Analysis." Journal of Chemical Information and Modeling 59, 5 (March 2019): 2199–2211 © 2019 American Chemical Society
Version
Original manuscript
Abstract
We investigate unexpectedly short non-covalent distances (<85% of the sum of van der Waals radii) in X-ray crystal structures of proteins. We curate over 11 000 high-quality protein crystal structures and an ultra-high-resolution (1.2 Å or better) subset containing >900 structures. Although our non-covalent distance criterion excludes standard hydrogen bonds known to be essential in protein stability, we observe over 75 000 close contacts (CCs) in the curated protein structures. Analysis of the frequency of amino acids participating in these interactions demonstrates some expected trends (i.e., enrichment of charged Lys, Arg, Asp, and Glu) but also reveals unexpected enhancement of Tyr in such interactions. Nearly all amino acids are observed to form at least one CC with all other amino acids, and most interactions are preserved in the much smaller ultra-high-resolution subset. We quantum-mechanically characterize the interaction energetics of a subset of >5000 CCs with symmetry-adapted perturbation theory to enable decomposition of interactions. We observe the majority of CCs to be favorable. The shortest favorable non-covalent distances are under 2.2 Å and are very repulsive when characterized with classical force fields. This analysis reveals stabilization by a combination of electrostatic and charge-transfer effects between hydrophobic (i.e., Val, Ile, Leu) amino acids and charged Asp or Glu. We also observe a unique hydrogen-bonding configuration between Tyr and Asn/Gln involving both residues acting simultaneously as hydrogen bond donors and acceptors. This work confirms the importance of first-principles simulation in explaining unexpected geometries in protein crystal structures.
MIT Department
Massachusetts Institute of Technology. Department of Chemical Engineering
Massachusetts Institute of Technology. Department of Chemistry
Terms of Use
Article is made available in accordance with the publisher's policy and may be subject to US copyright law. Please refer to the publisher's site for terms of use.
Persistent DSpace Link
DOI of Published Version
https://doi.org/10.1021/acs.jcim.9b00144
