title: Structures of the human Pals1 PDZ domain with and without ligand suggest gated access of Crb to the PDZ peptide-binding groove.
abstract: Many components of epithelial polarity protein complexes possess PDZ domains that are required for protein interaction and recruitment to the apical plasma membrane. Apical localization of the Crumbs (Crb) transmembrane protein requires a PDZ-mediated interaction with Pals1 (protein-associated with Lin7, Stardust, MPP5), a member of the p55 family of membrane-associated guanylate kinases (MAGUKs). This study describes the molecular interaction between the Crb carboxy-terminal motif (ERLI), which is required for Drosophila cell polarity, and the Pals1 PDZ domain using crystallography and fluorescence polarization. Only the last four Crb residues contribute to Pals1 PDZ-domain binding affinity, with specificity contributed by conserved charged interactions. Comparison of the Crb-bound Pals1 PDZ structure with an apo Pals1 structure reveals a key Phe side chain that gates access to the PDZ peptide-binding groove. Removal of this side chain enhances the binding affinity by more than fivefold, suggesting that access of Crb to Pals1 may be regulated by intradomain contacts or by protein-protein interaction.
authors.affiliation: Structural Biology Laboratories, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3LY, England.
authors.forename: Marina E
authors.initials: ME
authors.lastname: Ivanova
authors.affiliation: Epithelial Biology Laboratories, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3LY, England.
authors.forename: Georgina C
authors.initials: GC
authors.lastname: Fletcher
authors.affiliation: Peptide Chemistry Laboratories, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3LY, England.
authors.forename: Nicola
authors.initials: N
authors.lastname: O'Reilly
authors.affiliation: Structural Biology Laboratories, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3LY, England.
authors.forename: Andrew G
authors.initials: AG
authors.lastname: Purkiss
authors.affiliation: Epithelial Biology Laboratories, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3LY, England.
authors.forename: Barry J
authors.initials: BJ
authors.lastname: Thompson
authors.affiliation: Structural Biology Laboratories, Cancer Research UK, 44 Lincoln's Inn Fields, London WC2A 3LY, England.
authors.forename: Neil Q
authors.initials: NQ
authors.lastname: McDonald
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D029721:Drosophila Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster; D005136:Eye Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051528:Guanylate Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D009703:Nucleoside-Phosphate Kinase / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D020836:Protein Structure, Quaternary; D017434:Protein Structure, Tertiary
chemical_list: C448939:CRB1 protein, human; D029721:Drosophila Proteins; D005136:Eye Proteins; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; C064360:crb protein, Drosophila; D009703:Nucleoside-Phosphate Kinase; D051528:Guanylate Kinases; C501307:MPP5 protein, human; C444479:sdt protein, Drosophila
keywords: Crb; PDZ domains; cell polarity; epithelia; stardust