Structural and Functional Studies of FkpA from Escherichia coli, a cis/ trans Peptidyl-prolyl Isomerase with Chaperone Activity

• Published in: Journal of molecular biology Vol. 335; no. 2; pp. 595 - 608
• Main Authors: Saul, F.A., Arié, J.-P., Vulliez-le Normand, B., Kahn, R., Betton, J.-M., Bentley, G.A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 09.01.2004
• Subjects: Amino Acid Sequence; Bacterial Proteins - chemistry; Bacterial Proteins - metabolism; Binding Sites; Catalysis; chaperone; crystal structure; Crystallization; Crystallography, X-Ray; Dimerization; Escherichia coli; Escherichia coli - metabolism; Escherichia coli Proteins; FK506 complex; FKBP family; Immunophilins - chemistry; Immunophilins - metabolism; Ligands; Membrane Proteins - chemistry; Membrane Proteins - metabolism; Molecular Chaperones; Molecular Sequence Data; peptidyl-prolyl isomerase; Peptidylprolyl Isomerase; Periplasm; Protein Binding; Protein Conformation; Protein Folding; Protein Structure, Tertiary; Sequence Deletion; Sequence Homology, Amino Acid; Tacrolimus - metabolism; Tacrolimus Binding Proteins - chemistry; Tacrolimus Binding Proteins - metabolism; PPIase, peptidyl-prolyl isomerase; chaperone; LpMIP, Legionella pneumophila Macrophage Infectivity Potentiator; rms, root mean square; TcMIP, Trypanosoma cruzi Macrophage Infectivity Potentiator; crystal structure; FKBP, FK506-binding protein; peptidyl-prolyl isomerase; FKBP family; FK506 complex
• ISSN: 0022-2836; 1089-8638
• DOI: 10.1016/j.jmb.2003.10.056

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.