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Title: Crystal structure and conformational flexibility of the unligated FK506-binding protein FKBP12.6

Two crystal forms of unligated FKBP12.6 exhibit multiple conformations in the active site and in the 80s loop, the primary site for known protein-recognition interactions. The previously unreported NMR backbone assignment of FKBP12.6 revealed extensive doubling of amide resonances, which reflects a slow conformational transition centered in the 80s loop. The primary known physiological function of FKBP12.6 involves its role in regulating the RyR2 isoform of ryanodine receptor Ca{sup 2+} channels in cardiac muscle, pancreatic β islets and the central nervous system. With only a single previously reported X-ray structure of FKBP12.6, bound to the immunosuppressant rapamycin, structural inferences for this protein have been drawn from the more extensive studies of the homologous FKBP12. X-ray structures at 1.70 and 1.90 Å resolution from P2{sub 1} and P3{sub 1}21 crystal forms are reported for an unligated cysteine-free variant of FKBP12.6 which exhibit a notable diversity of conformations. In one monomer from the P3{sub 1}21 crystal form, the aromatic ring of Phe59 at the base of the active site is rotated perpendicular to its typical orientation, generating a steric conflict for the immunosuppressant-binding mode. The peptide unit linking Gly89 and Val90 at the tip of the protein-recognition ‘80s loop’ is flipped inmore » the P2{sub 1} crystal form. Unlike the >30 reported FKBP12 structures, the backbone conformation of this loop closely follows that of the first FKBP domain of FKBP51. The NMR resonances for 21 backbone amides of FKBP12.6 are doubled, corresponding to a slow conformational transition centered near the tip of the 80s loop, as recently reported for 31 amides of FKBP12. The comparative absence of doubling for residues along the opposite face of the active-site pocket in FKBP12.6 may in part reflect attenuated structural coupling owing to increased conformational plasticity around the Phe59 ring.« less
Authors:
;  [1] ;  [1] ;  [2] ;  [1] ;  [3] ; ;  [1] ;  [2]
  1. New York State Department of Health, Empire State Plaza, Albany, NY 12201 (United States)
  2. (United States)
  3. Brookhaven National Laboratory, Upton, NY 11973 (United States)
Publication Date:
OSTI Identifier:
22347783
Resource Type:
Journal Article
Resource Relation:
Journal Name: Acta Crystallographica. Section D: Biological Crystallography; Journal Volume: 70; Journal Issue: Pt 3; Other Information: PMCID: PMC3949516; PMID: 24598733; PUBLISHER-ID: kw5080; OAI: oai:pubmedcentral.nih.gov:3949516; Copyright (c) Chen et al. 2014; This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
Denmark
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; ALLOCATIONS; COUPLING; CRYSTAL STRUCTURE; CRYSTALS; CYSTEINE; FLEXIBILITY; INTERACTIONS; MONOMERS; NUCLEAR MAGNETIC RESONANCE; ORIENTATION; PLASTICITY; RECEPTORS; RESOLUTION; RINGS