Structural basis for assembly of the Mn(IV)/Fe(III) cofactor in the class Ic ribonucleotide reductase from Chlamydia trachomatis.
Structural basis for assembly of the Mn(IV)/Fe(III) cofactor in the class Ic ribonucleotide reductase from Chlamydia trachomatis.
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DOI：
10.1021/bi400819x
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发表时间：
2013-09-17
期刊：
影响因子：
2.9
通讯作者：
Boal, Amie K.
中科院分区：
文献类型：
--
作者：
Dassama, Laura M. K.;Krebs, Carsten;Bollinger, J. Martin, Jr.;Rosenzweig, Amy C.;Boal, Amie K.
沙眼衣原体（Ct）的Ic类核糖核苷酸还原酶（RNR）在其β2亚基的每个单体中使用MnIV/FeIII辅因子来启动核苷酸还原。辅因子通过MnII/FeII-β2与O2反应形成。以前，载脂蛋白β2和二价金属离子的体外辅因子组装产生了两种形式的混合物，Mn在位点1（MnIV/FeIII）或位点2（FeIII/MnIV），其中活性更高的MnIV/FeIII产物占主导地位。在这里，我们通过求解Ct β2的apo、MnII和MnII/FeII复合物的X射线晶体结构，解决了金属位点选择性的基础。厌氧获得的结构与等摩尔MnII，FeII，和载脂蛋白揭示独家纳入MnII在网站1和FeII在网站2中，相比之下，以前实现的更温和的位点选择性。位点特异性由载脂蛋白结构控制，因为在金属结合时仅发生配体的微小调整。额外的结构意味着，本身，锰II结合在任一网站。这些结构与体外辅因子组装的模型一致，其中FeII对位点2的特异性驱动适当配置的异源中心的组装，前提是FeII是亚化学计量的。该模型表明，在体内使用MnIV/FeIII辅因子可能是对FeII限制的适应。MnII/FeII-β2复合物的1.8 μ m分辨率模型揭示了辅因子活化的其他结构决定因素，包括O2与FeII的侧边（η2）加成位点和短（3.2 μ m）MnII-FeII电子距离，促进MnIV/FeIV活化中间体的形成。
The class Ic ribonucleotide reductase (RNR) from Chlamydia trachomatis (Ct) employs a MnIV/FeIII cofactor in each monomer of its β2 subunit to initiate nucleotide reduction. The cofactor forms by reaction of MnII/FeII-β2 with O2. Previously, in vitro cofactor assembly from apo β2 and divalent metal ions produced a mixture of two forms, with Mn in site 1 (MnIV/FeIII) or site 2 (FeIII/MnIV), of which the more active MnIV/FeIII product predominates. Here we have addressed the basis for metal site-selectivity by solving X-ray crystal structures of apo, MnII, and MnII/FeII complexes of Ct β2. A structure obtained anaerobically with equimolar MnII, FeII, and apo protein reveals exclusive incorporation of MnII in site 1 and FeII in site 2, in contrast to the more modest site-selectivity achieved previously. Site-specificity is controlled thermodynamically by the apo protein structure, as only minor adjustments of ligands occur upon metal binding. Additional structures imply that, by itself, MnII binds in either site. Together the structures are consistent with a model for in vitro cofactor assembly in which FeII specificity for site 2 drives assembly of the appropriately configured heterobimetallic center, provided that FeII is substoichiometric. This model suggests that use of an MnIV/FeIII cofactor in vivo could be an adaptation to FeII limitation. A 1.8 Å resolution model of the MnII/FeII-β2 complex reveals additional structural determinants for activation of the cofactor, including a proposed site for side-on (η2) addition of O2 to FeII and a short (3.2 Å) MnII-FeII interionic distance, promoting formation of the MnIV/FeIV activation intermediate.
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影响因子：
56.9
作者：
Högbom, M;Stenmark, P;Nordlund, P
通讯作者：
Nordlund, P
DOI：
10.1107/s0907444904019158
发表时间：
2004-12-01
影响因子：
2.2
作者：
Emsley, P;Cowtan, K
通讯作者：
Cowtan, K
影响因子：
2.9
作者：
Högbom, M;Huque, Y;Nordlund, P
通讯作者：
Nordlund, P
DOI：
10.1107/s0907444909042073
发表时间：
2010-01
期刊：
Acta crystallographica. Section D, Biological crystallography
影响因子：
--
作者：
Chen VB;Arendall WB 3rd;Headd JJ;Keedy DA;Immormino RM;Kapral GJ;Murray LW;Richardson JS;Richardson DC
通讯作者：
Richardson DC
DOI：
10.1073/pnas.1220341110
发表时间：
2013-03-05
影响因子：
11.1
作者：
Damo, Steven M.;Kehl-Fie, Thomas E.;Chazin, Walter J.
通讯作者：
Chazin, Walter J.