title: Structural characterization of a unique interface between carbohydrate response element-binding protein (ChREBP) and 14-3-3β protein.
abstract: Carbohydrate response element-binding protein (ChREBP) is an insulin-independent, glucose-responsive transcription factor that is expressed at high levels in liver hepatocytes where it plays a critical role in converting excess carbohydrates to fat for storage. In response to fluctuating glucose levels, hepatic ChREBP activity is regulated in large part by nucleocytoplasmic shuttling of ChREBP protein via interactions with 14-3-3 proteins. The N-terminal ChREBP regulatory region is necessary and sufficient for glucose-responsive ChREBP nuclear import and export. Here, we report the crystal structure of a complex of 14-3-3β bound to the N-terminal regulatory region of ChREBP at 2.4 Å resolution. The crystal structure revealed that the α2 helix of ChREBP (residues 117-137) adopts a well defined α-helical conformation and binds 14-3-3 in a phosphorylation-independent manner that is different from all previously characterized 14-3-3 and target protein-binding modes. ChREBP α2 interacts with 14-3-3 through both electrostatic and van der Waals interactions, and the binding is partially mediated by a free sulfate or phosphate. Structure-based mutagenesis and binding assays indicated that disrupting the observed 14-3-3 and ChREBP α2 interface resulted in a loss of complex formation, thus validating the novel protein interaction mode in the 14-3-3β·ChREBP α2 complex.
authors.affiliation: Department of Biochemistry, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390, USA.
authors.forename: Qiang
authors.initials: Q
authors.lastname: Ge
authors.forename: Nian
authors.initials: N
authors.lastname: Huang
authors.forename: R Max
authors.initials: RM
authors.lastname: Wynn
authors.forename: Yang
authors.initials: Y
authors.lastname: Li
authors.forename: Xinlin
authors.initials: X
authors.lastname: Du
authors.forename: Bonnie
authors.initials: B
authors.lastname: Miller
authors.forename: Hong
authors.initials: H
authors.lastname: Zhang
authors.forename: Kosaku
authors.initials: K
authors.lastname: Uyeda
mesh_terms: D048948:14-3-3 Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D000818:Animals; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018360:Crystallography, X-Ray; D051379:Mice; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D049790:Nuclear Export Signals; D019913:Nuclear Localization Signals / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D010449:Peptide Mapping; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017433:Protein Structure, Secondary; D014157:Transcription Factors / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D048948:14-3-3 Proteins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; C506001:Mlxipl protein, mouse; D046912:Multiprotein Complexes; D049790:Nuclear Export Signals; D019913:Nuclear Localization Signals; D009687:Nuclear Proteins; D014157:Transcription Factors