title: Resolving the functions of peptidylprolyl isomerases: insights from the mutagenesis of the nuclear FKBP25 enzyme.
abstract: Peptidylprolyl isomerases have been implicated in chromatin regulation through their association with histones, chromatin-modifying enzymes and DNA-binding transcription factors. As with other post-translational modifications to proteins, a mechanistic understanding of the regulation of biological processes is fostered by loss-of-function studies both in vitro and in vivo. For peptidylprolyl isomerases, this can be accomplished with small-molecule inhibitors with high affinity for the isomerase active site or by mutation of amino acid residues that contribute to catalysis. In the present article, we review caveats to each of these approaches, and place emphasis on the thorough characterization of loss-of-function mutations in FKBPs (FK506-binding proteins). Using a case study of mutagenesis of the nuclear FKBP25 peptidylprolyl isomerase enzyme, we demonstrate that certain mutations generate a loss-of-function phenotype because they induce a complete loss of the FKBP domain fold, whereas other mutations are 'surgical' in that they ablate catalytic isomerase activity, while maintaining domain structure. Peptidylprolyl isomerases are thought to have both catalytic and non-catalytic functions, but differentiating between these mechanisms has proved to be challenging. The domain-destabilizing and surgical mutants described will facilitate the characterization of these two reported functions of peptidylprolyl isomerases.
authors.affiliation: Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC, Canada V8W 3P6.
authors.forename: Geoff
authors.initials: G
authors.lastname: Gudavicius
authors.forename: Heddy
authors.initials: H
authors.lastname: Soufari
authors.forename: Santosh Kumar
authors.initials: SK
authors.lastname: Upadhyay
authors.forename: Santosh
authors.initials: S
authors.lastname: Upadhyay
authors.forename: Cameron D
authors.initials: CD
authors.lastname: Mackereth
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Nelson
mesh_terms: D000818:Animals; D002467:Cell Nucleus / Q000201:enzymology / Q000378:metabolism; D006801:Humans; D008958:Models, Molecular; D016297:Mutagenesis, Site-Directed; D009154:Mutation / Q000502:physiology; D017510:Protein Folding; D054730:Protein Interaction Domains and Motifs / Q000235:genetics / Q000502:physiology; D013329:Structure-Activity Relationship; D022021:Tacrolimus Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*
chemical_list: C074856:FKBP3 protein, human; D022021:Tacrolimus Binding Proteins