Role of allosteric: zinc interdomain region of the regulatory subunit in the allosteric regulation of aspartate transcarbamoylase from Escherichia coli.
Role of allosteric: zinc interdomain region of the regulatory subunit in the allosteric regulation of aspartate transcarbamoylase from Escherichia coli.
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变构的作用：调节亚基的锌域间区域在大肠杆菌天冬氨酸转氨甲酰酶的变构调节中的作用。
DOI：
10.1006/abbi.1998.0692
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发表时间：
1998
期刊：
影响因子：
--
通讯作者：
Wild,JR
中科院分区：
文献类型：
--
作者：
Rastogi,VK;Swanson,R;Hartberg,YM;Wales,ME;Wild,JR
之前已经发现天冬氨酸氨甲酰转移酶调节亚基的变构域和锌域之间的疏水界面参与了该酶的异向性ATP活化。目前的工作表明，这个接口也影响CTP和CTP-UTP抑制，并提出了一个结构的解释的影响。来自残基r101-r106（残基，贡献的接口的一部分）的非选择性诱变的突变体酶显示出各种同向和异向效应。V106 L、V106 L/N105 S和I103 F/R102 C的表观Hill系数值和降低的Δ S0.5值表明，酶的协同行为受到影响。此外，在这些突变体中，ATP激活和CTP抑制均显著降低，CTP+UTP协同抑制降低。D104 G突变体酶受CTP和CTP +UTP的抑制，但不受ATP的激活。最后，I103 T突变酶的S0.5值增加到11.5 mM，并显示出改变的效应器反应：ATP作为抑制剂，CTP+UTP协同抑制作用降低。这些变构变异中的大多数可以解释为对变构和锌结构域之间的“舌和沟”疏水界面的扰动以及对调节和催化亚基之间的第二界面（“reg 1：cat 4”）的后续影响。
The hydrophobic interface between the allosteric and the zinc domains of the regulatory subunit of aspartate transcarbamoylase has previously been implicated in the heterotropic ATP activation of the enzyme. The present work shows that this interface also affects CTP and CTP–UTP inhibition and proposes a structural explanation for the effects. Mutant enzymes derived from nonselective mutagenesis of residues r101–r106 (residues that contribute part of the interface) displayed a variety of homotropic and heterotropic effects. The cooperative behavior of the enzymes was affected, as indicated by reduced aspartateS0.5values and apparent Hill coefficient values for V106L, V106L/N105S, and I103F/R102C. In addition, both ATP activation and CTP inhibition were significantly reduced and CTP+UTP synergistic inhibition was decreased in these mutants. The D104G mutant enzyme was subject to inhibition by CTP andCTP+UTP, but was not activated by ATP. Finally, the I103T mutant enzyme had an increasedS0.5value of 11.5 mM and displayed altered effector responses: ATP acted as an inhibitor, and the CTP+UTP synergistic inhibition was reduced. Most of these allosteric variations can be explained in terms of perturbations to the “tongue and groove” hydrophobic interface between the allosteric and the zinc domains and a consequent impact on a second interface (“reg1:cat4”) between regulatory and catalytic subunits.