Engineering protein stability with atomic precision in a monomeric miniprotein
Emily G Baker, Christopher Williams, Kieran L Hudson, Gail J Bartlett, Jack W Heal, Kathryn L Porter Goff, Richard B Sessions, Matthew P Crump & Derek N Woolfson
AffiliationsContributionsCorresponding authors
Nature Chemical Biology (2017) doi:10.1038/nchembio.2380
Received 20 September 2016 Accepted 27 February 2017 Published online 22 May 2017
Source/Fonte: Emily G. Baker et al.
Abstract
Miniproteins simplify the protein-folding problem, allowing the dissection of forces that stabilize protein structures. Here we describe PPα-Tyr, a designed peptide comprising an α-helix buttressed by a polyproline II helix. PPα-Tyr is water soluble and monomeric, and it unfolds cooperatively with a midpoint unfolding temperature (TM) of 39 °C. NMR structures of PPα-Tyr reveal proline residues docked between tyrosine side chains, as designed. The stability of PPα is sensitive to modifications in the aromatic residues: replacing tyrosine with phenylalanine, i.e., changing three solvent-exposed hydroxyl groups to protons, reduces the TM to 20 °C. We attribute this result to the loss of CH–π interactions between the aromatic and proline rings, which we probe by substituting the aromatic residues with nonproteinogenic side chains. In analyses of natural protein structures, we find a preference for proline–tyrosine interactions over other proline-containing pairs, and observe abundant CH–π interactions in biologically important complexes between proline-rich ligands and SH3 and similar domains.
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