1SO6

Crystal structure of E112Q/H136A double mutant of 3-keto-L-gulonate 6-phosphate decarboxylase with bound L-threonohydroxamate 4-phosphate

1SO6 の概要

• エントリーDOI: 10.2210/pdb1so6/pdb
• 関連するPDBエントリー: 1Q6L 1Q6O 1Q6Q 1Q6R 1SO3 1SO4 1SO5
• 分子名称: 3-keto-L-gulonate 6-phosphate decarboxylase, MAGNESIUM ION, L-THREONOHYDROXAMATE 4-PHOSPHATE, ... (4 entities in total)
• 機能のキーワード: tim barrel; beta barrel, lyase
• 由来する生物種: Escherichia coli
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 47584.81

構造登録者

Wise, E.L.,Yew, W.S.,Gerlt, J.A.,Rayment, I. (登録日: 2004-03-12, 公開日: 2004-06-08, 最終更新日: 2024-11-13)

主引用文献

Wise, E.L.,Yew, W.S.,Gerlt, J.A.,Rayment, I.
Evolution of Enzymatic Activities in the Orotidine 5'-Monophosphate Decarboxylase Suprafamily: Crystallographic Evidence for a Proton Relay System in the Active Site of 3-Keto-l-gulonate 6-Phosphate Decarboxylase(,)
Biochemistry, 43:6438-6446, 2004

PubMed Abstract: 3-Keto-L-gulonate 6-phosphate decarboxylase (KGPDC), a member of the orotidine monophosphate decarboxylase (OMPDC) suprafamily, catalyzes the Mg(2+)-dependent decarboxylation of 3-keto-L-gulonate 6-phosphate to L-xylulose 5-phosphate. Structural and biochemical evidence suggests that the KGPDC reaction proceeds via a Mg(2+)-stabilized 1,2-cis-enediolate intermediate. Protonation of the enediolate intermediate occurs in a nonstereospecific manner to form L-xylulose 5-phosphate. Although the exact mechanism of proton delivery is not known, Glu112, His136, and Arg139 have been implicated in this process [Yew, W. S., Wise, E., Rayment, I., and Gerlt, J. A. (2004) Biochemistry 43, 6427-6437]. Surprisingly, single amino acid substitutions of these positions do not substantially reduce catalytic activity but rather alter the stereochemical course of the reaction. Here, we report the X-ray crystal structures of four mutants, K64A, H136A, E112Q, and E112Q/H136A, each determined in the presence of L-threonohydroxamate 4-phosphate, an analogue of the enediolate intermediate, to 1.7, 1.9, 1.8, and 1.9 A resolution, respectively. These structures reveal that substitutions of Lys64, Glu112, and His136 cause changes in the positions of the intermediate analogue and two active site water molecules that were previously identified as possible proton donors. These changes correlate with the observed alterations in the reaction stereochemistry for these mutants, thereby supporting a reaction mechanism in which water molecules competitively shuttle protons from the side chains of His136 and Arg139 to alternate faces of the cis-enediolate intermediate. These studies further underscore the wide variation in the reaction mechanisms in the OMPDC suprafamily.

PubMed: 15157078
DOI: 10.1021/bi0497392

実験手法

X-RAY DIFFRACTION (1.902 Å)