A prototypical cytidylyltransferase: CTP:glycerol-3-phosphate cytidylyltransferase from bacillus subtilis.
A prototypical cytidylyltransferase: CTP:glycerol-3-phosphate cytidylyltransferase from bacillus subtilis.
复制标题
原型胞苷酰转移酶：CTP：来自枯草芽孢杆菌的甘油-3-磷酸胞苷酰转移酶。
DOI：
10.1016/s0969-2126(99)80178-6
复制
发表时间：
1999
期刊：
影响因子：
--
通讯作者：
Ludwig,ML
中科院分区：
文献类型：
--
作者：
Weber,CH;Park,YS;Sanker,S;Kent,C;Ludwig,ML
背景：脂质和复合碳水化合物生物合成中关键中间体的形成由胞苷酰转移酶进行，胞苷酰转移酶利用CTP形成活化的CDP-醇或CMP-酸性糖加无机焦磷酸盐。几种胞苷酰转移酶是相关的，并构成保守的酶家族。该家族的真核成员是具有多个调节区或重复催化结构域的复杂酶，而细菌酶CTP：甘油-3-磷酸胞苷酰转移酶（GCT）仅包含催化结构域。结果：用汞衍生物多波长反常衍射法测定了枯草芽孢杆菌GCT的晶体结构，并将其分辨率提高到2.0 μ m（R因子0.196; Rfree0.255）。GCT是同二聚体;每个单体包含具有中心3-2-1-4-5平行β折叠的α/β折叠。从α/β核心延伸的额外螺旋和环形成结合底物的碗。CTP结合在同源二聚体的每个活性位点上，与保守的14 HXGH和113 RTXGISTT基序相互作用。二聚体接口采用了第三个基序，63 RYVDEVI的一部分，并包括邻接的HXGH sequence.Conclusions：结构叠加涉及GCT的催化结构域从I类氨酰-tRNA synthetases，从而扩大tRNA合成酶家族的折叠，包括催化结构域的胞苷酰转移酶家族。GCT和氨酰-tRNA合成酶催化类似的反应，以类似的U形构象结合核苷酸，并依赖于来自类似HXGH基序的组氨酸的活性。结构和其他相似性支持GCT像合成酶一样通过稳定CTP的α-磷酸的五价过渡态来催化核苷酸转移的提议。
Background:The formation of critical intermediates in the biosynthesis of lipids and complex carbohydrates is carried out by cytidylyltransferases, which utilize CTP to form activated CDP-alcohols or CMP-acid sugars plus inorganic pyrophosphate. Several cytidylyltransferases are related and constitute a conserved family of enzymes. The eukaryotic members of the family are complex enzymes with multiple regulatory regions or repeated catalytic domains, whereas the bacterial enzyme, CTP:glycerol-3-phosphate cytidylyltransferase (GCT), contains only the catalytic domain. Thus, GCT provides an excellent model for the study of catalysis by the eukaryotic cytidylyltransferases.Results:The crystal structure of GCT fromBacillus subtilishas been determined by multiwavelength anomalous diffraction using a mercury derivative and refined to 2.0 Å resolution (Rfactor0.196; Rfree0.255). GCT is a homodimer; each monomer comprises anα/βfold with a central 3-2-1-4-5 parallelβsheet. Additional helices and loops extending from theα/βcore form a bowl that binds substrates. CTP, bound at each active site of the homodimer, interacts with the conserved14HXGH and113RTXGISTT motifs. The dimer interface incorporates part of a third motif,63RYVDEVI, and includes hydrophobic residues adjoining the HXGH sequence.Conclusions:Structure superpositions relate GCT to the catalytic domains from class I aminoacyl-tRNA synthetases, and thus expand the tRNA synthetase family of folds to include the catalytic domains of the family of cytidylyltransferases. GCT and aminoacyl-tRNA synthetases catalyze analogous reactions, bind nucleotides in similar U-shaped conformations, and depend on histidines from analogous HXGH motifs for activity. The structural and other similarities support proposals that GCT, like the synthetases, catalyzes nucleotidyl transfer by stabilizing a pentavalent transition state at theα-phosphate of CTP.