title: Structural basis of ligand recognition by PABC, a highly specific peptide-binding domain found in poly(A)-binding protein and a HECT ubiquitin ligase.
abstract: The C-terminal domain of poly(A)-binding protein (PABC) is a peptide-binding domain found in poly(A)-binding proteins (PABPs) and a HECT (homologous to E6-AP C-terminus) family E3 ubiquitin ligase. In protein synthesis, the PABC domain of PABP functions to recruit several translation factors possessing the PABP-interacting motif 2 (PAM2) to the mRNA poly(A) tail. We have determined the solution structure of the human PABC domain in complex with two peptides from PABP-interacting protein-1 (Paip1) and Paip2. The structures show a novel mode of peptide recognition, in which the peptide binds as a pair of beta-turns with extensive hydrophobic, electrostatic and aromatic stacking interactions. Mutagenesis of PABC and peptide residues was used to identify key protein-peptide interactions and quantified by isothermal calorimetry, surface plasmon resonance and GST pull-down assays. The results provide insight into the specificity of PABC in mediating PABP-protein interactions.
authors.affiliation: Department of Biochemistry, McGill University, 3655 Promenade Sir William Osler, Montreal, Quebec, Canada.
authors.forename: Guennadi
authors.initials: G
authors.lastname: Kozlov
authors.forename: Gregory
authors.initials: G
authors.lastname: De Crescenzo
authors.forename: Nadia S
authors.initials: NS
authors.lastname: Lim
authors.forename: Nadeem
authors.initials: N
authors.lastname: Siddiqui
authors.forename: Daniel
authors.initials: D
authors.lastname: Fantus
authors.forename: Avak
authors.initials: A
authors.lastname: Kahvejian
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Trempe
authors.forename: Demetra
authors.initials: D
authors.lastname: Elias
authors.forename: Irena
authors.initials: I
authors.lastname: Ekiel
authors.forename: Nahum
authors.initials: N
authors.lastname: Sonenberg
authors.forename: Maureen
authors.initials: M
authors.lastname: O'Connor-McCourt
authors.forename: Kalle
authors.initials: K
authors.lastname: Gehring
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D001665:Binding Sites; D002352:Carrier Proteins / Q000737:chemistry / Q000378:metabolism; D017124:Conserved Sequence; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D008958:Models, Molecular; D008969:Molecular Sequence Data; D019906:Nuclear Magnetic Resonance, Biomolecular; D010448:Peptide Initiation Factors / Q000737:chemistry / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000378:metabolism; D039102:Poly(A)-Binding Proteins / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D012269:Ribosomal Proteins / Q000737:chemistry*; D055672:Static Electricity; D044767:Ubiquitin-Protein Ligases / Q000737:chemistry*
chemical_list: D002352:Carrier Proteins; D008024:Ligands; C111580:PAIP1 protein, human; C488448:PAIP2 protein, human; D010448:Peptide Initiation Factors; D010455:Peptides; D039102:Poly(A)-Binding Proteins; D016601:RNA-Binding Proteins; D012097:Repressor Proteins; D012269:Ribosomal Proteins; C117617:UBR5 protein, human; D044767:Ubiquitin-Protein Ligases