Structural insights into the catalytic mechanism of a sacrificial sulfur insertase of the N-type ATP pyrophosphatase family, LarE
Structural insights into the catalytic mechanism of a sacrificial sulfur insertase of the N-type ATP pyrophosphatase family, LarE
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DOI：
10.1073/pnas.1704967114
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发表时间：
2017-08-22
影响因子：
11.1
通讯作者：
Hu, Jian
中科院分区：
文献类型：
--
作者：
Fellner, Matthias;Desguin, Benoit;Hu, Jian
植物乳杆菌中的 lar 操纵子编码五种 Lar 蛋白 (LarA/B/C/D/E)，这些蛋白协同合成烟酸衍生的含 Ni 辅因子并将其整合到 LarA（一种 Ni 依赖性乳酸消旋酶）中。先前的研究已经证实，LarE 的两个分子通过将其独有的半胱氨酸残基的硫原子贡献给底物来催化连续的硫醇化反应。然而，这种非常不寻常的硫牺牲反应的催化机制仍然难以捉摸。在这项工作中，我们展示了 LarE 无配体和几种配体结合形式的晶体结构，证明 LarE 是 N 型 ATP 焦磷酸酶 (PPase) 家族的成员，具有保守的 N 端 ATP PPase 结构域和具有假定催化位点的独特 C 端结构域。结构分析与结构引导诱变相结合，使我们提出了一种催化机制，将 LarE 建立为通过牺牲其催化半胱氨酸残基进行硫转移的范例。
The lar operon in Lactobacillus plantarum encodes five Lar proteins (LarA/B/C/D/E) that collaboratively synthesize and incorporate a niacin-derived Ni-containing cofactor into LarA, an Ni-dependent lactate racemase. Previous studies have established that two molecules of LarE catalyze successive thiolation reactions by donating the sulfur atom of their exclusive cysteine residues to the substrate. However, the catalytic mechanism of this very unusual sulfur-sacrificing reaction remains elusive. In this work, we present the crystal structures of LarE in ligand-free and several ligand-bound forms, demonstrating that LarE is a member of the N-type ATP pyrophosphatase (PPase) family with a conserved N-terminal ATP PPase domain and a unique C-terminal domain harboring the putative catalytic site. Structural analysis, combined with structure-guided mutagenesis, leads us to propose a catalytic mechanism that establishes LarE as a paradigm for sulfur transfer through sacrificing its catalytic cysteine residue.