3AX9

Bovine xanthine oxidase, protease cleaved form

3AX9 の概要

• エントリーDOI: 10.2210/pdb3ax9/pdb
• 関連するPDBエントリー: 3AX7
• 分子名称: Xanthine dehydrogenase/oxidase, FE2/S2 (INORGANIC) CLUSTER, FLAVIN-ADENINE DINUCLEOTIDE, ... (9 entities in total)
• 機能のキーワード: oxidoreductase
• 由来する生物種: Bos taurus (bovine)
• 細胞内の位置: Cytoplasm (By similarity): P80457
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 298308.26

構造登録者

Ishikita, H.,Eger, B.T.,Pai, E.F.,Okamoto, K.,Nishino, T. (登録日: 2011-03-31, 公開日: 2012-02-22, 最終更新日: 2024-03-13)

主引用文献

Ishikita, H.,Eger, B.T.,Okamoto, K.,Nishino, T.,Pai, E.F.
Protein conformational gating of enzymatic activity in xanthine oxidoreductase
J.Am.Chem.Soc., 134:999-1009, 2012

PubMed Abstract: In mammals, xanthine oxidoreductase can exist as xanthine dehydrogenase (XDH) and xanthine oxidase (XO). The two enzymes possess common redox active cofactors, which form an electron transfer (ET) pathway terminated by a flavin cofactor. In spite of identical protein primary structures, the redox potential difference between XDH and XO for the flavin semiquinone/hydroquinone pair (E(sq/hq)) is ~170 mV, a striking difference. The former greatly prefers NAD(+) as ultimate substrate for ET from the iron-sulfur cluster FeS-II via flavin while the latter only accepts dioxygen. In XDH (without NAD(+)), however, the redox potential of the electron donor FeS-II is 180 mV higher than that for the acceptor flavin, yielding an energetically uphill ET. On the basis of new 1.65, 2.3, 1.9, and 2.2 Å resolution crystal structures for XDH, XO, the NAD(+)- and NADH-complexed XDH, E(sq/hq) were calculated to better understand how the enzyme activates an ET from FeS-II to flavin. The majority of the E(sq/hq) difference between XDH and XO originates from a conformational change in the loop at positions 423-433 near the flavin binding site, causing the differences in stability of the semiquinone state. There was no large conformational change observed in response to NAD(+) binding at XDH. Instead, the positive charge of the NAD(+) ring, deprotonation of Asp429, and capping of the bulk surface of the flavin by the NAD(+) molecule all contribute to altering E(sq/hq) upon NAD(+) binding to XDH.

PubMed: 22145797
DOI: 10.1021/ja207173p

実験手法

X-RAY DIFFRACTION (2.3 Å)