title: Structural and functional studies of FkpA from Escherichia coli, a cis/trans peptidyl-prolyl isomerase with chaperone activity.
abstract: The protein FkpA from the periplasm of Escherichia coli exhibits both cis/trans peptidyl-prolyl isomerase (PPIase) and chaperone activities. The crystal structure of the protein has been determined in three different forms: as the full-length native molecule, as a truncated form lacking the last 21 residues, and as the same truncated form in complex with the immunosuppressant ligand, FK506. FkpA is a dimeric molecule in which the 245-residue subunit is divided into two domains. The N-terminal domain includes three helices that are interlaced with those of the other subunit to provide all inter-subunit contacts maintaining the dimeric species. The C-terminal domain, which belongs to the FK506-binding protein (FKBP) family, binds the FK506 ligand. The overall form of the dimer is V-shaped, and the different crystal structures reveal a flexibility in the relative orientation of the two C-terminal domains located at the extremities of the V. The deletion mutant FkpNL, comprising the N-terminal domain only, exists in solution as a mixture of monomeric and dimeric species, and exhibits chaperone activity. By contrast, a deletion mutant comprising the C-terminal domain only is monomeric, and although it shows PPIase activity, it is devoid of chaperone function. These results suggest that the chaperone and catalytic activities reside in the N and C-terminal domains, respectively. Accordingly, the observed mobility of the C-terminal domains of the dimeric molecule could effectively adapt these two independent folding functions of FkpA to polypeptide substrates.
authors.affiliation: Unité d'Immunologie Structurale (C.N.R.S. U.R.A. 2185), Institut Pasteur, 25 rue du Dr Roux, 75724 Paris cedex 15, France.
authors.forename: F A
authors.initials: FA
authors.lastname: Saul
authors.forename: J-P
authors.initials: JP
authors.lastname: Arié
authors.forename: B
authors.initials: B
authors.lastname: Vulliez-le Normand
authors.forename: R
authors.initials: R
authors.lastname: Kahn
authors.forename: J-M
authors.initials: JM
authors.lastname: Betton
authors.forename: G A
authors.initials: GA
authors.lastname: Bentley
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001665:Binding Sites; D002384:Catalysis; D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D004926:Escherichia coli / Q000378:metabolism; D029968:Escherichia coli Proteins; D020104:Immunophilins / Q000737:chemistry* / Q000378:metabolism; D008024:Ligands; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D018832:Molecular Chaperones; D008969:Molecular Sequence Data; D019696:Peptidylprolyl Isomerase; D019897:Periplasm; D011485:Protein Binding; D011487:Protein Conformation; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D016559:Tacrolimus / Q000378:metabolism*; D022021:Tacrolimus Binding Proteins / Q000737:chemistry / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D029968:Escherichia coli Proteins; D008024:Ligands; D008565:Membrane Proteins; D018832:Molecular Chaperones; D022021:Tacrolimus Binding Proteins; D020104:Immunophilins; D019696:Peptidylprolyl Isomerase; C068254:FkpA protein, E coli; D016559:Tacrolimus