Bacterial chalcone isomerase complexed with naringenin

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.163 
  • R-Value Work: 0.140 
  • R-Value Observed: 0.141 

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Structure and Catalytic Mechanism of the Evolutionarily Unique Bacterial Chalcone Isomerase

Thomsen, M.Tuukkanen, A.Dickerhoff, J.Palm, G.J.Kratzat, H.Svergun, D.I.Weisz, K.Bornscheuer, U.T.Hinrichs, W.

(2015) Acta Crystallogr D Biol Crystallogr 71: 907

  • DOI: https://doi.org/10.1107/S1399004715001935
  • Primary Citation of Related Structures:  
    4C9S, 4C9T, 4D06

  • PubMed Abstract: 

    Flavonoids represent a large class of secondary metabolites produced by plants. These polyphenolic compounds are well known for their antioxidative abilities, are antimicrobial phytoalexins responsible for flower pigmentation to attract pollinators and, in addition to other properties, are also specific bacterial regulators governing the expression of Rhizobium genes involved in root nodulation (Firmin et al., 1986). The bacterial chalcone isomerase (CHI) from Eubacterium ramulus catalyses the first step in a flavanone-degradation pathway by ring opening of (2S)-naringenin to form naringenin chalcone. The structural biology and enzymology of plant CHIs have been well documented, whereas the existence of bacterial CHIs has only recently been elucidated. This first determination of the structure of a bacterial CHI provides detailed structural insights into the key step of the flavonoid-degradation pathway. The active site could be confirmed by co-crystallization with the substrate (2S)-naringenin. The stereochemistry of the proposed mechanism of the isomerase reaction was verified by specific (1)H/(2)H isotope exchange observed by (1)H NMR experiments and was further supported by mutagenesis studies. The active site is shielded by a flexible lid, the varying structure of which could be modelled in different states of the catalytic cycle using small-angle X-ray scattering data together with the crystallographic structures. Comparison of bacterial CHI with the plant enzyme from Medicago sativa reveals that they have unrelated folds, suggesting that the enzyme activity evolved convergently from different ancestor proteins. Despite the lack of any functional relationship, the tertiary structure of the bacterial CHI shows similarities to the ferredoxin-like fold of a chlorite dismutase and the stress-related protein SP1.

  • Organizational Affiliation

    Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Strasse 4, 17489 Greifswald, Germany.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
A, B, C, D, E
A, B, C, D, E, F
283Eubacterium ramulusMutation(s): 0 
Find proteins for V9P0A9 (Eubacterium ramulus)
Explore V9P0A9 
Go to UniProtKB:  V9P0A9
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupV9P0A9
Sequence Annotations
  • Reference Sequence
Small Molecules
Ligands 4 Unique
IDChains Name / Formula / InChI Key2D Diagram3D Interactions
Query on X8W

Download Ideal Coordinates CCD File 
J [auth B],
T [auth D]
C15 H12 O5
Query on NAR

Download Ideal Coordinates CCD File 
CA [auth F]
DA [auth F]
G [auth A]
N [auth C]
R [auth D]
CA [auth F],
DA [auth F],
G [auth A],
N [auth C],
R [auth D],
S [auth D],
X [auth E]
C15 H12 O5
Query on GOL

Download Ideal Coordinates CCD File 
EA [auth F],
K [auth B]
C3 H8 O3
Query on CL

Download Ideal Coordinates CCD File 
AA [auth E]
BA [auth E]
FA [auth F]
GA [auth F]
H [auth A]
AA [auth E],
BA [auth E],
FA [auth F],
GA [auth F],
H [auth A],
HA [auth F],
I [auth A],
L [auth B],
M [auth B],
O [auth C],
P [auth C],
Q [auth C],
U [auth D],
V [auth D],
W [auth D],
Y [auth E],
Z [auth E]
Experimental Data & Validation

Experimental Data

  • Resolution: 2.00 Å
  • R-Value Free: 0.163 
  • R-Value Work: 0.140 
  • R-Value Observed: 0.141 
  • Space Group: I 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 181.165α = 90
b = 187.991β = 90
c = 196.221γ = 90
Software Package:
Software NamePurpose
XDSdata reduction
XDSdata scaling

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2015-04-08
    Type: Initial release
  • Version 1.1: 2015-04-22
    Changes: Database references
  • Version 1.2: 2023-12-20
    Changes: Data collection, Database references, Derived calculations, Other, Refinement description