2VZK

Structure of the acyl-enzyme complex of an N-terminal nucleophile (Ntn) hydrolase, OAT2

2VZK の概要

• エントリーDOI: 10.2210/pdb2vzk/pdb
• 関連するPDBエントリー: 1VZ6 1VZ7 1VZ8
• 分子名称: GLUTAMATE N-ACETYLTRANSFERASE 2 ALPHA CHAIN, GLUTAMATE N-ACETYLTRANSFERASE 2 BETA CHAIN, 2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL, ... (6 entities in total)
• 機能のキーワード: acyl enzyme, transferase, ntn hydrolase, acyltransferase
• 由来する生物種: STREPTOMYCES CLAVULIGERUS; 詳細
• タンパク質・核酸の鎖数: 8
• 化学式量合計: 164183.89

構造登録者

Iqbal, A.,Clifton, I.J.,Schofield, C.J. (登録日: 2008-08-01, 公開日: 2008-09-16, 最終更新日: 2024-11-13)

主引用文献

Iqbal, A.,Clifton, I.J.,Bagonis, M.,Kershaw, N.J.,Domene, C.,Claridge, T.D.,Wharton, C.W.,Schofield, C.J.
Anatomy of a Simple Acyl Intermediate in Enzyme Catalysis: Combined Biophysical and Modeling Studies on Ornithine Acetyl Transferase.
J.Am.Chem.Soc., 131:749-, 2009

PubMed Abstract: Acyl-enzyme complexes are intermediates in reactions catalyzed by many hydrolases and related enzymes which employ nucleophilic catalysis. However, most of the reported structural data on acyl-enzyme complexes has been acquired under noncatalytic conditions. Recent IR analyses have indicated that some acyl-enzyme complexes may be more flexible than most crystallographic analyses have implied. OAT2 is a member of the N-terminal nucleophile (Ntn) hydrolase enzyme superfamily and catalyzes the reversible transfer of an acetyl group between the alpha-amino groups of ornithine and glutamate in a mechanism proposed to involve an acyl-enzyme complex. We have carried out biophysical analyses on ornithine acetyl transferase (OAT2), both in solution and in the crystalline state. Mass spectrometric studies identified Thr-181 as the residue acetylated during OAT2 catalysis; (13)C NMR analyses implied the presence of an acyl-enzyme complex in solution. Crystallization of OAT2 in the presence of N-alpha-acetyl-L-glutamate led to a structure in which Thr-181 was acetylated; the carbonyl oxygen of the acyl-enzyme complex was located in an oxyanion hole and positioned to hydrogen bond with the backbone amide NH of Gly-112 and the alcohol of Thr-111. While the crystallographic analyses revealed only one structure, IR spectroscopy demonstrated the presence of two distinct acyl-enzyme complex structures with carbonyl stretching frequencies at 1691 and 1701 cm(-1). Modeling studies implied two possible acyl-enzyme complex structures, one of which correlates with that observed in the crystal structure and with the 1691 cm(-1) IR absorption. The second acyl-enzyme complex structure, which has only a single oxyanion hole hydrogen bond, is proposed to give rise to the 1701 cm(-1) IR absorption. The two acyl-enzyme complex structures can interconvert by movement of the Thr-111 side-chain alcohol hydrogen away from the oxyanion hole to hydrogen bond with the backbone carbonyl of the acylated residue, Thr-181. Overall, the results reveal that acyl-enzyme complex structures may be more dynamic than previously thought and support the use of a comprehensive biophysical and modeling approach in studying such intermediates.

PubMed: 19105697
DOI: 10.1021/JA807215U

実験手法

X-RAY DIFFRACTION (2.33 Å)