A cross-strand Trp–Trp pair stabilizes the hPin1 WW domain at the expense of function
Document Type
Article
Publication Date
10-2007
Publisher
John Wiley & Sons, Inc
Abstract
Using the human Pin1 WW domain (hPin1 WW), we show that replacement of two nearest neighbor non-hydrogen-bonded residues on adjacent β-strands with tryptophan (Trp) residues increases β-sheet thermodynamic stability by 4.8 kJ mol−1 at physiological temperature. One-dimensional NMR studies confirmed that introduction of the Trp–Trp pair does not globally perturb the structure of the triple-stranded β-sheet, while circular dichroism studies suggest that the engineered cross-strand Trp–Trp pair adopts a side-chain conformation similar to that first reported for a designed “Trp-zipper” β-hairpin peptide, wherein the indole side chains stack perpendicular to each other. Even though the mutated side chains in wild-type hPin1 WW are not conserved among WW domains and compose the β-sheet surface opposite to that responsible for ligand binding, introduction of the cross-strand Trp–Trp pair effectively eliminates hPin1 WW function as assessed by the loss of binding affinity toward a natural peptide ligand. Maximizing both thermodynamic stability and the domain function of hPin1 WW by the above mentioned approach appears to be difficult, analogous to the situation with loop 1 optimization explored previously. That introduction of a non-hydrogen-bonded cross-strand Trp–Trp pair within the hPin1 WW domain eliminates function may provide a rationale for why this energetically favorable pairwise interaction has not yet been identified in WW domains or any other biologically evolved protein with known three-dimensional structure.
Recommended Citation
Jäger, M., Dendle, M., Fuller, A. A., & Kelly, J. W. (2007). A cross-strand Trp–Trp pair stabilizes the hPin1 WW domain at the expense of function. Protein Science, 16(10), 2306–2313. https://doi.org/10.1110/ps.072904107
