ジャーナル: Acta Crystallogr D Biol Crystallogr / 年: 2015 タイトル: Structure and catalytic mechanism of the evolutionarily unique bacterial chalcone isomerase. 著者: Maren Thomsen / Anne Tuukkanen / Jonathan Dickerhoff / Gottfried J Palm / Hanna Kratzat / Dmitri I Svergun / Klaus Weisz / Uwe T Bornscheuer / Winfried Hinrichs / 要旨: Flavonoids represent a large class of secondary metabolites produced by plants. These polyphenolic compounds are well known for their antioxidative abilities, are antimicrobial phytoalexins ...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.
#1: ジャーナル: Arch.Microbiol. / 年: 2004 タイトル: First Bacterial Chalcone Isomerase Isolated from Eubacterium Ramulus. 著者: Herles, C. / Braune, A. / Blaut, M.
解像度: 1.8→48.07 Å / Cor.coef. Fo:Fc: 0.975 / Cor.coef. Fo:Fc free: 0.968 / SU B: 3.048 / SU ML: 0.042 / 交差検証法: THROUGHOUT / ESU R: 0.064 / ESU R Free: 0.065 / 立体化学のターゲット値: MAXIMUM LIKELIHOOD 詳細: HYDROGENS HAVE BEEN ADDED IN THE RIDING POSITIONS. U VALUES WITH TLS ADDED
Rfactor
反射数
%反射
Selection details
Rfree
0.15389
15464
5 %
RANDOM
Rwork
0.13446
-
-
-
obs
0.13544
293803
99.57 %
-
溶媒の処理
イオンプローブ半径: 0.8 Å / 減衰半径: 0.8 Å / VDWプローブ半径: 1.2 Å / 溶媒モデル: MASK