Crystal structure of p38alpha in complex with a photoswitchable 2-Azothiazol-based Inhibitor (compound 2)

Experimental Data Snapshot

  • Resolution: 2.30 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.191 
  • R-Value Observed: 0.193 

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This is version 1.3 of the entry. See complete history


2-Azo-, 2-diazocine-thiazols and 2-azo-imidazoles as photoswitchable kinase inhibitors: limitations and pitfalls of the photoswitchable inhibitor approach.

Schehr, M.Ianes, C.Weisner, J.Heintze, L.Muller, M.P.Pichlo, C.Charl, J.Brunstein, E.Ewert, J.Lehr, M.Baumann, U.Rauh, D.Knippschild, U.Peifer, C.Herges, R.

(2019) Photochem Photobiol Sci 18: 1398-1407

  • DOI: https://doi.org/10.1039/c9pp00010k
  • Primary Citation of Related Structures:  
    6HMP, 6HMR, 6HWT, 6HWU, 6HWV

  • PubMed Abstract: 

    In photopharmacology, photoswitchable compounds including azobenzene or other diarylazo moieties exhibit bioactivity against a target protein typically in the slender E-configuration, whereas the rather bulky Z-configuration usually is pharmacologically less potent. Herein we report the design, synthesis and photochemical/inhibitory characterization of new photoswitchable kinase inhibitors targeting p38α MAPK and CK1δ. A well characterized inhibitor scaffold was used to attach arylazo- and diazocine moieties. When the isolated isomers, or the photostationary state (PSS) of isomers, were tested in commonly used in vitro kinase assays, however, only small differences in activity were observed. X-ray analyses of ligand-bound p38α MAPK and CK1δ complexes revealed dynamic conformational adaptations of the protein with respect to both isomers. More importantly, irreversible reduction of the azo group to the corresponding hydrazine was observed. Independent experiments revealed that reducing agents such as DTT (dithiothreitol) and GSH (glutathione) that are typically used for protein stabilization in biological assays were responsible. Two further sources of error are the concentration dependence of the E-Z-switching efficiency and artefacts due to incomplete exclusion of light during testing. Our findings may also apply to a number of previously investigated azobenzene-based photoswitchable inhibitors.

  • Organizational Affiliation

    Otto Diels-Institute of Organic Chemistry, Christian Albrechts University Kiel, Otto-Hahn-Platz 4, 24118 Kiel, Germany. rherges@oc.uni-kiel.de.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Mitogen-activated protein kinase 14362Homo sapiensMutation(s): 0 
UniProt & NIH Common Fund Data Resources
Find proteins for Q16539 (Homo sapiens)
Explore Q16539 
Go to UniProtKB:  Q16539
GTEx:  ENSG00000112062 
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupQ16539
Sequence Annotations
  • Reference Sequence
Small Molecules
Binding Affinity Annotations 
IDSourceBinding Affinity
GE5 Binding MOAD:  6HWU IC50: 54.7 (nM) from 1 assay(s)
Experimental Data & Validation

Experimental Data

  • Resolution: 2.30 Å
  • R-Value Free: 0.247 
  • R-Value Work: 0.191 
  • R-Value Observed: 0.193 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 66.67α = 90
b = 74.69β = 90
c = 77.24γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XSCALEdata scaling

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
German Federal Ministry for Education and ResearchGermanyBMBF 01GS08104
German Federal Ministry for Education and ResearchGermany01ZX1303C

Revision History  (Full details and data files)

  • Version 1.0: 2019-04-17
    Type: Initial release
  • Version 1.1: 2019-06-19
    Changes: Data collection, Database references
  • Version 1.2: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Derived calculations, Structure summary
  • Version 1.3: 2024-01-24
    Changes: Data collection, Database references, Refinement description, Structure summary