2HIM

Crystal Structure and Allosteric Regulation of the Cytoplasmic Escherichia coli L-Asparaginase I

2HIM の概要

• エントリーDOI: 10.2210/pdb2him/pdb
• 関連するPDBエントリー: 2P2D 2P2N
• 分子名称: L-asparaginase 1, ASPARTIC ACID, ASPARAGINE, ... (5 entities in total)
• 機能のキーワード: asparaginase, hydrolase
• 由来する生物種: Escherichia coli
• 細胞内の位置: Cytoplasm: P0A962
• タンパク質・核酸の鎖数: 4
• 化学式量合計: 159307.64

構造登録者

Yun, M.K.,Nourse, A.,White, S.W.,Rock, C.O.,Heath, R.J. (登録日: 2006-06-29, 公開日: 2007-05-15, 最終更新日: 2024-10-30)

主引用文献

Yun, M.K.,Nourse, A.,White, S.W.,Rock, C.O.,Heath, R.J.
Crystal Structure and Allosteric Regulation of the Cytoplasmic Escherichia coli L-Asparaginase I.
J.Mol.Biol., 369:794-811, 2007

PubMed Abstract: AnsA is the cytoplasmic asparaginase from Escherichia coli involved in intracellular asparagine utilization. Analytical ultracentifugation and X-ray crystallography reveal that AnsA forms a tetrameric structure as a dimer of two intimate dimers. Kinetic analysis of the enzyme reveals that AnsA is positively cooperative, displaying a sigmoidal substrate dependence curve with an [S](0.5) of 1 mM L-asparagine and a Hill coefficient (n(H)) of 2.6. Binding of L-asparagine to an allosteric site was observed in the crystal structure concomitant with a reorganization of the quarternary structure, relative to the apo enzyme. The carboxyl group of the bound asparagine makes salt bridges and hydrogen bonds to Arg240, while the N(delta2) nitrogen interacts with Thr162. Mutation of Arg240 to Ala increases the [S](0.5) value to 5.9 mM, presumably by reducing the affinity of the site for L-asparagine, although the enzyme retains cooperativity. Mutation of Thr162 to Ala results in an active enzyme with no cooperativity. Transmission of the signal from the allosteric site to the active site appears to involve subtle interactions at the dimer-dimer interface and relocation of Gln118 into the vicinity of the active site to position the probable catalytic water molecule. These data define the structural basis for the cooperative regulation of the intracellular asparaginase that is required for proper functioning within the cell.

PubMed: 17451745
DOI: 10.1016/j.jmb.2007.03.061

実験手法

X-RAY DIFFRACTION (1.82 Å)