1NBE

ASPARTATE TRANSCARBAMOYLASE REGULATORY CHAIN MUTANT (T82A)

1NBE の概要

• エントリーDOI: 10.2210/pdb1nbe/pdb
• 分子名称: ASPARTATE TRANSCARBAMOYLASE, D-MALATE, ZINC ION, ... (5 entities in total)
• 機能のキーワード: atcase, allostery, pyrimidine biosynthesis, transferase
• 由来する生物種: Escherichia coli; 詳細
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 103568.58

構造登録者

Williams, M.K.,Stec, B.,Kantrowitz, E.R. (登録日: 1998-04-25, 公開日: 1998-10-14, 最終更新日: 2024-05-22)

主引用文献

Williams, M.K.,Stec, B.,Kantrowitz, E.R.
A single mutation in the regulatory chain of Escherichia coli aspartate transcarbamoylase results in an extreme T-state structure.
J.Mol.Biol., 281:121-134, 1998

PubMed Abstract: Kinetic analysis of a mutant version of Escherichia coli aspartate transcarbamoylase in which Thr82 in the regulatory chain (Thr82r) was replaced by Ala results in a shift in the T <==> R equilibrium towards the T-state. In order to understand the structural determinants of this T-state stabilization, the X-ray structure of the unliganded Thr82r-->Ala enzyme was determined at 2. 6 A resolution and refined to a crystallographic residual of 0.175. The structure of the mutant r1 regulatory chain is more similar to that of the r6 regulatory chain than observed for the wild-type enzyme, resulting in a more symmetric structure. Furthermore, the structural changes in the mutant enzyme appears to occur only in the r1 chain, while the r6 chain is almost identical in structure to that of the r6 chain of the wild-type enzyme. The structure of the mutant enzyme exhibits alterations in the subunit interfaces between the regulatory and catalytic chains, as well as in the interface between the allosteric and zinc domains within the regulatory chain. Moreover, the regulatory dimers are rotated around their respective 2-fold axes approximately 1 degrees beyond the rotation which occurs in the wild-type T-state enzyme. The structural analysis indicates that the enzyme is an "extreme" T-state, in which a larger rotation of the regulatory dimers is required for the T to R transition compared to the wild-type enzyme. This extreme T-state structure correlates well with the kinetic parameters determined for the mutant enzyme, showing a stabilized T-state. Furthermore, the structural analysis of the mutant enzyme suggests that replacement of Thr82r with Ala alters the local conformation of the nucleotide binding pocket and therefore offers a plausible explanation for the reduced affinity of the enzyme for nucleotides.

PubMed: 9680480
DOI: 10.1006/jmbi.1998.1923

実験手法

X-RAY DIFFRACTION (2.6 Å)