4wrq

Publication Abstract from PubMed

The partially disordered Chibby (Cby) is a conserved nuclear protein that antagonizes the Wnt/beta-catenin signaling pathway. By competing with the Tcf/Lef family proteins for binding to beta-catenin, Cby abrogates the beta-catenin-mediated transcription of Wnt signaling genes. Additionally, upon phosphorylation on S20 by the kinase Akt, Cby forms a complex with 14-3-3 to facilitate the nuclear export of beta-catenin, which represents another crucial mechanism for the regulation of Wnt signaling. To obtain a mechanistic understanding of the 14-3-3/Cby interaction, we have extensively characterized the complex using X-ray crystallography, nuclear magnetic resonance (NMR) spectroscopy, and isothermal titration calorimetry (ITC). The crystal structure of the human 14-3-3zeta/Cby protein-peptide complex reveals a canonical binding mode; however the residue at the +2 position from the phosphorylated serine is shown to be uniquely oriented relative to other solved structures of 14-3-3 complexes. Our ITC results illustrate that although the phosphorylation of S20 is essential for Cby to recognize 14-3-3, residues flanking the phosphorylation site also contribute to the binding affinity. However, as is commonly observed in other 14-3-3/phosphopeptide crystal structures, residues of Cby flanking the 14-3-3 binding motif lack observable electron density. To obtain a more detailed binding interface, we have completed the backbone NMR resonance assignment of 14-3-3zeta. NMR titration experiments reveal that residues outside of the 14-3-3 conserved binding cleft, namely a flexible loop consisting of residues 203-210, are also involved in binding Cby. By using a combined X-ray and NMR approach, we have dissected the molecular basis of the 14-3-3/Cby interaction.

Structural Analysis of the 14-3-3zeta/Chibby Interaction Involved in Wnt/beta-Catenin Signaling.,Killoran RC, Fan J, Yang D, Shilton BH, Choy WY PLoS One. 2015 Apr 24;10(4):e0123934. doi: 10.1371/journal.pone.0123934., eCollection 2015. PMID:25909186^[6]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.