title: A cross-strand Trp Trp pair stabilizes the hPin1 WW domain at the expense of function.
abstract: Using the human Pin1 WW domain (hPin1 WW), we show that replacement of two nearest neighbor non-hydrogen-bonded residues on adjacent beta-strands with tryptophan (Trp) residues increases beta-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 beta-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" beta-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 beta-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.
authors.affiliation: Department of Chemistry, Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Marcus
authors.initials: M
authors.lastname: Jäger
authors.forename: Maria
authors.initials: M
authors.lastname: Dendle
authors.forename: Amelia A
authors.initials: AA
authors.lastname: Fuller
authors.forename: Jeffery W
authors.initials: JW
authors.lastname: Kelly
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D019906:Nuclear Magnetic Resonance, Biomolecular; D019696:Peptidylprolyl Isomerase / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D013050:Spectrometry, Fluorescence; D013816:Thermodynamics; D014364:Tryptophan / Q000737:chemistry*
chemical_list: D008024:Ligands; D000072340:NIMA-Interacting Peptidylprolyl Isomerase; D014364:Tryptophan; C000606846:PIN1 protein, human; D019696:Peptidylprolyl Isomerase