4C9T

BACTERIAL CHALCONE ISOMERASE IN open CONFORMATION FROM EUBACTERIUM RAMULUS AT 2.0 A RESOLUTION, SelenoMet derivative

Summary for 4C9T

• Entry DOI: 10.2210/pdb4c9t/pdb
• Related: 4C9S
• Descriptor: CHALCONE ISOMERASE, GLYCEROL, CHLORIDE ION, ... (5 entities in total)
• Functional Keywords: isomerase, flavonoids
• Biological source: EUBACTERIUM RAMULUS
• Total number of polymer chains: 6
• Total formula weight: 198153.16

Authors

Thomsen, M.,Palm, G.J.,Hinrichs, W. (deposition date: 2013-10-03, release date: 2014-10-22, Last modification date: 2024-11-06)

Primary citation

Thomsen, M.,Tuukkanen, A.,Dickerhoff, J.,Palm, G.J.,Kratzat, H.,Svergun, D.I.,Weisz, K.,Bornscheuer, U.T.,Hinrichs, W.
Structure and Catalytic Mechanism of the Evolutionarily Unique Bacterial Chalcone Isomerase
Acta Crystallogr.,Sect.D, 71:907-, 2015

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.

PubMed: 25849401
DOI: 10.1107/S1399004715001935

Experimental method

X-RAY DIFFRACTION (1.98 Å)