title: Crystal structure and functional analysis of the protein disulfide isomerase-related protein ERp29.
abstract: The protein disulfide isomerase-related protein ERp29 is a putative chaperone involved in processing and secretion of secretory proteins. Until now, however, both the structure and the exact nature of interacting substrates remained unclear. We provide for the first time a crystal structure of human ERp29, refined to 2.9 A, and show that the protein has considerable structural homology to its Drosophila homolog Wind. We show that ERp29 binds directly not only to thyroglobulin and thyroglobulin-derived peptides in vitro but also to the Wind client protein Pipe and Pipe-derived peptides, although it fails to process Pipe in vivo. A monomeric mutant of ERp29 and a D domain mutant in which the second peptide binding site is inactivated also bind protein substrates, indicating that the monomeric thioredoxin domain is sufficient for client protein binding. Indeed, the b domains of ERp29 or Wind, expressed alone, are sufficient for binding proteins and peptides. Interacting peptides have in common two or more aromatic residues, with stronger binding for sequences with overall basic character. Thus, the data allow a view of the two putative peptide binding sites of ERp29 and indicate that the apparent, different processing activity of the human and Drosophila proteins in vivo does not stem from differences in peptide binding properties.
authors.affiliation: Max Planck Research Unit for Enzymology of Protein Folding, Halle (Saale), Germany.
authors.forename: Naomi N
authors.initials: NN
authors.lastname: Barak
authors.forename: Piotr
authors.initials: P
authors.lastname: Neumann
authors.forename: Madhumati
authors.initials: M
authors.lastname: Sevvana
authors.forename: Mike
authors.initials: M
authors.lastname: Schutkowski
authors.forename: Kai
authors.initials: K
authors.lastname: Naumann
authors.forename: Miroslav
authors.initials: M
authors.lastname: Malesević
authors.forename: Heike
authors.initials: H
authors.lastname: Reichardt
authors.forename: Gunter
authors.initials: G
authors.lastname: Fischer
authors.forename: Milton T
authors.initials: MT
authors.lastname: Stubbs
authors.forename: David M
authors.initials: DM
authors.lastname: Ferrari
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D018360:Crystallography, X-Ray; D019281:Dimerization; D029721:Drosophila Proteins / Q000737:chemistry; D006360:Heat-Shock Proteins / Q000737:chemistry* / Q000235:genetics; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009154:Mutation; D010455:Peptides / Q000737:chemistry; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D013379:Substrate Specificity; D013879:Thioredoxins / Q000737:chemistry; D013954:Thyroglobulin / Q000737:chemistry
chemical_list: D029721:Drosophila Proteins; C491738:ERP29 protein, human; D006360:Heat-Shock Proteins; D010455:Peptides; D013879:Thioredoxins; D013954:Thyroglobulin