5JXZ

A low magnesium structure of the isochorismate synthase, EntC

5JXZ の概要

• エントリーDOI: 10.2210/pdb5jxz/pdb
• 関連するPDBエントリー: 5JY4 5JY8 5JY9
• 分子名称: Isochorismate synthase EntC, MAGNESIUM ION, (5S,6S)-5-[(1-carboxyethenyl)oxy]-6-hydroxycyclohexa-1,3-diene-1-carboxylic acid, ... (5 entities in total)
• 機能のキーワード: chorismate, isochorismate, isomerase
• 由来する生物種: Escherichia coli O157:H7
• タンパク質・核酸の鎖数: 2
• 化学式量合計: 86906.28

構造登録者

Meneely, K.M.,Sundlov, J.A.,Gulick, A.M.,Lamb, A.L. (登録日: 2016-05-13, 公開日: 2016-07-20, 最終更新日: 2023-09-27)

主引用文献

Meneely, K.M.,Sundlov, J.A.,Gulick, A.M.,Moran, G.R.,Lamb, A.L.
An Open and Shut Case: The Interaction of Magnesium with MST Enzymes.
J.Am.Chem.Soc., 138:9277-9293, 2016

PubMed Abstract: The shikimate pathway of bacteria, fungi, and plants generates chorismate, which is drawn into biosynthetic pathways that form aromatic amino acids and other important metabolites, including folates, menaquinone, and siderophores. Many of the pathways initiated at this branch point transform chorismate using an MST enzyme. The MST enzymes (menaquinone, siderophore, and tryptophan biosynthetic enzymes) are structurally homologous and magnesium-dependent, and all perform similar chemical permutations to chorismate by nucleophilic addition (hydroxyl or amine) at the 2-position of the ring, inducing displacement of the 4-hydroxyl. The isomerase enzymes release isochorismate or aminodeoxychorismate as the product, while the synthase enzymes also have lyase activity that displaces pyruvate to form either salicylate or anthranilate. This has led to the hypothesis that the isomerase and lyase activities performed by the MST enzymes are functionally conserved. Here we have developed tailored pre-steady-state approaches to establish the kinetic mechanisms of the isochorismate and salicylate synthase enzymes of siderophore biosynthesis. Our data are centered on the role of magnesium ions, which inhibit the isochorismate synthase enzymes but not the salicylate synthase enzymes. Prior structural data have suggested that binding of the metal ion occludes access or egress of substrates. Our kinetic data indicate that for the production of isochorismate, a high magnesium ion concentration suppresses the rate of release of product, accounting for the observed inhibition and establishing the basis of the ordered-addition kinetic mechanism. Moreover, we show that isochorismate is channeled through the synthase reaction as an intermediate that is retained in the active site by the magnesium ion. Indeed, the lyase-active enzyme has 3 orders of magnitude higher affinity for the isochorismate complex relative to the chorismate complex. Apparent negative-feedback inhibition by ferrous ions is documented at nanomolar concentrations, which is a potentially physiologically relevant mode of regulation for siderophore biosynthesis in vivo.

PubMed: 27373320
DOI: 10.1021/jacs.6b05134

実験手法

X-RAY DIFFRACTION (1.88 Å)