title: Active site mutants of human cyclophilin A separate peptidyl-prolyl isomerase activity from cyclosporin A binding and calcineurin inhibition.
abstract: Based on recent X-ray structural information, six site-directed mutants of human cyclophilin A (hCyPA) involving residues in the putative active site--H54, R55, F60, Q111, F113, and H126--have been constructed, overexpressed, and purified from Escherichia coli to homogeneity. The proteins W121A (Liu, J., Chen, C.-M., & Walsh, C.T., 1991a, Biochemistry 30, 2306-2310), H54Q, R55A, F60A, Q111A, F113A, and H126Q were assayed for cis-trans peptidyl-prolyl isomerase (PPIase) activity, their ability to bind the immunosuppressive drug cyclosporin A (CsA), and protein phosphatase 2B (calcineurin) inhibition in the presence of CsA. Results indicate that H54Q, Q111A, F113A, and W121A retain 3-15% of the catalytic efficiency (kcat/Km) of wild-type recombinant hCyPA. The remaining three mutants (R55A, F60A, and H126Q) each retain less than 1% of the wild-type catalytic efficiency, indicating participation by these residues in PPIase catalysis. Each of the mutants bound to a CsA affinity matrix. The mutants R55A, F60A, F113A, and H126Q inhibited calcineurin in the presence of CsA, whereas W121A did not. Although CsA is a competitive inhibitor of PPIase activity, it can complex with enzymatically inactive cyclophilins and inhibit the phosphatase activity of calcineurin.
authors.affiliation: Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts 02115.
authors.forename: L D
authors.initials: LD
authors.lastname: Zydowsky
authors.forename: F A
authors.initials: FA
authors.lastname: Etzkorn
authors.forename: H Y
authors.initials: HY
authors.lastname: Chang
authors.forename: S B
authors.initials: SB
authors.lastname: Ferguson
authors.forename: L A
authors.initials: LA
authors.lastname: Stolz
authors.forename: S I
authors.initials: SI
authors.lastname: Ho
authors.forename: C T
authors.initials: CT
authors.lastname: Walsh
mesh_terms: D000591:Amino Acid Isomerases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites; D019703:Calcineurin; D002148:Calmodulin-Binding Proteins / Q000494:pharmacology*; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002942:Circular Dichroism; D016572:Cyclosporine / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009838:Oligodeoxyribonucleotides; D019696:Peptidylprolyl Isomerase; D010749:Phosphoprotein Phosphatases / Q000494:pharmacology*; D011485:Protein Binding; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011994:Recombinant Proteins / Q000737:chemistry / Q000378:metabolism; D013050:Spectrometry, Fluorescence
chemical_list: D002148:Calmodulin-Binding Proteins; D002352:Carrier Proteins; D009838:Oligodeoxyribonucleotides; D011994:Recombinant Proteins; D016572:Cyclosporine; D019703:Calcineurin; D010749:Phosphoprotein Phosphatases; D000591:Amino Acid Isomerases; D019696:Peptidylprolyl Isomerase