A Structural Ensemble for the Enzyme Cyclophilin Reveals an Orchestrated Mode of Action at Atomic Resolution.
For enzyme activity, an exact structural and motional orchestration of the active site and its surroundings is believed to be key. In order to reveal such possible phenomena at atomic resolution on the basis of experimental evidence, an experimental restraint driven two-state ensemble of the prototypical enzyme cyclophilin was determined by using a recently introduced exact NOE approach. The ensemble description reveals the presence of an open and a closed state of cyclophilin, which is indicative of large-scale correlated motion. In the open state, the catalytic site is preorganized for catalysis, thus suggesting the mechanism of action to be conformational sampling, while the ligand-binding loop appears to act through an induced fit mechanism. This finding is supported by affinity measurements of a cyclophilin designed to be more open. Overall, more than 60-70 % of the side-chain conformations of cyclophilin appear to be correlated.
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland).
Celestine N
CN
Chi
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland).
Beat
B
Vögeli
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland).
Stefan
S
Bibow
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland).
Dean
D
Strotz
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland).
Julien
J
Orts
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland).|Institute of Biophysical Chemistry, Center for Biomolecular Magnetic Resonance, Goethe University Frankfurt am Main, Max-von-Laue-Strasse 9, 60438 Frankfurt am Main (Germany).
Peter
P
Güntert
Laboratory of Physical Chemistry, ETH Zurich, ETH-Hönggerberg, 8093 Zürich (Switzerland). roland.riek@phys.chem.ethz.ch.
Roland
R
Riek
D055162:Biocatalysis; D021983:Cyclophilins / Q000737:chemistry* / Q000378:metabolism*; D004789:Enzyme Activation; D008958:Models, Molecular; D011487:Protein Conformation
D021983:Cyclophilins
NMR spectroscopy; biophysics; enzyme mechanisms; enzymes; protein structures