Engineering protein stability with atomic precision in a monomeric miniprotein.

ABSTRACT: Miniproteins simplify the protein-folding problem, allowing the dissection of forces that stabilize protein structures. Here we describe PP?-Tyr, a designed peptide comprising an ?-helix buttressed by a polyproline II helix. PP?-Tyr is water soluble and monomeric, and it unfolds cooperatively with a midpoint unfolding temperature (TM) of 39 °C. NMR structures of PP?-Tyr reveal proline residues docked between tyrosine side chains, as designed. The stability of PP? 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-? 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-? interactions in biologically important complexes between proline-rich ligands and SH3 and similar domains.

SUBMITTER: Baker EG 

PROVIDER: S-EPMC5860740 | biostudies-literature | 2017 Jul

REPOSITORIES: biostudies-literature