title: Incorporating beta-turns and a turn mimetic out of context in loop 1 of the WW domain affords cooperatively folded beta-sheets.
abstract: To probe the conformational requirements of loop 1 in the Pin1 WW domain, the residues at the i + 2 and i + 3 positions of a beta-turn within this loop were replaced by dPro-Gly and Asn-Gly, which are known to prefer the conformations required at the i + 1 and i + 2 positions of type II' and type I' beta-turns. Conformational specificity or lack thereof was further examined by incorporating into the i + 2 and i + 3 positions a non-alpha-amino acid-based beta-turn mimetic (4-(2'-aminoethyl)-6-dibenzofuran propionic acid residue, 1), which was designed to replace the i + 1 and i + 2 positions of beta-turns. All these Pin WW variants are monomeric and folded as discerned by analytical ultracentrifugation, NMR, and CD. They exhibit cooperative two-state transitions and display thermodynamic stability within 0.5 kcal/mol of the wild-type WW domain, demonstrating that the acquisition of native structure and stability does not require a specific sequence and, by extension, conformation within loop 1. However, it could be that these loop 1 mutations alter the kinetics of antiparallel beta-sheet folding, which will be addressed by subsequent kinetic studies.
authors.affiliation: Contribution from the Department of Chemistry and The Skaggs Institute for Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, BCC 506, La Jolla, California 92037, USA.
authors.forename: R
authors.initials: R
authors.lastname: Kaul
authors.forename: A R
authors.initials: AR
authors.lastname: Angeles
authors.forename: M
authors.initials: M
authors.lastname: Jäger
authors.forename: E T
authors.initials: ET
authors.lastname: Powers
authors.forename: J W
authors.initials: JW
authors.lastname: Kelly
mesh_terms: D000595:Amino Acid Sequence; D002942:Circular Dichroism; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D018716:Molecular Mimicry; D008969:Molecular Sequence Data; D017510:Protein Folding; D011506:Proteins / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D011506:Proteins