Mycobacteria Encode Active and Inactive Classes of TesB Fatty-Acyl CoA Thioesterases Revealed through Structural and Functional Analysis.
Mycobacteria Encode Active and Inactive Classes of TesB Fatty-Acyl CoA Thioesterases Revealed through Structural and Functional Analysis.
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DOI：
10.1021/acs.biochem.6b01049
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发表时间：
2017-03
期刊：
影响因子：
2.9
通讯作者：
C. Swarbrick;Glennon V Bythrow;D. Aragão;Gabrielle A Germain;L. Quadri;J. Forwood
中科院分区：
文献类型：
--
作者：
C. Swarbrick;Glennon V Bythrow;D. Aragão;Gabrielle A Germain;L. Quadri;J. Forwood
分枝杆菌含有大量高度分化的物种，并表现出不寻常的脂质代谢特征，据信在免疫入侵中发挥重要作用。硫酯酶通过水解活化的脂肪酰辅酶A来调节脂质代谢；分枝杆菌中存在多个拷贝，但许多拷贝仍未被表征。在这里，我们对鸟分枝杆菌 (MaTesB) 的 TesB 硫酯酶进行了全面的结构和功能分析。与其他 TesB 硫酯酶的结构叠加表明，在多种 TesB 硫酯酶中高度保守的 Asp 活性位点残基突变为 Ala。与这些结构数据一致，野生型酶未能水解多种酰基辅酶 A 底物。该残基突变为活性天冬氨酸残基恢复了针对一系列中链长度脂肪酰基 CoA 底物的活性。有趣的是，这种 Ala 突变在多种分枝杆菌属物种中高度保守，但在任何其他细菌或生物体中都没有发现。我们的结构同源性分析表明，至少另一种 TesB 酰基辅酶 A 硫酯酶在活性位点也含有 Ala 残基，而另外两种分枝杆菌 TesB 硫酯酶在活性位点含有 Asp 残基。无活性的 TesB 显示出与活性 TesB 硫酯酶不同的常见四级结构。据我们所知，对耻垢分枝杆菌中催化活性或无活性 MaTesB 表达效果的研究揭示了第一个涉及分枝杆菌 tesB 基因的基因型-表型关联。这是分枝杆菌编码活性和非活性形式的硫酯酶的第一份报告，后者似乎是分枝杆菌所独有的。
Mycobacteria contain a large number of highly divergent species and exhibit unusual lipid metabolism profiles, believed to play important roles in immune invasion. Thioesterases modulate lipid metabolism through the hydrolysis of activated fatty-acyl CoAs; multiple copies are present in mycobacteria, yet many remain uncharacterized. Here, we undertake a comprehensive structural and functional analysis of a TesB thioesterase from Mycobacterium avium (MaTesB). Structural superposition with other TesB thioesterases reveals that the Asp active site residue, highly conserved across a wide range of TesB thioesterases, is mutated to Ala. Consistent with these structural data, the wild-type enzyme failed to hydrolyze an extensive range of acyl-CoA substrates. Mutation of this residue to an active Asp residue restored activity against a range of medium-chain length fatty-acyl CoA substrates. Interestingly, this Ala mutation is highly conserved across a wide range of Mycobacterium species but not found in any other bacteria or organism. Our structural homology analysis revealed that at least one other TesB acyl-CoA thioesterase also contains an Ala residue at the active site, while two other Mycobacterium TesB thioesterases harbor an Asp residue at the active site. The inactive TesBs display a common quaternary structure that is distinct from that of the active TesB thioesterases. Investigation of the effect of expression of either the catalytically active or inactive MaTesB in Mycobacterium smegmatis exposed, to the best of our knowledge, the first genotype-phenotype association implicating a mycobacterial tesB gene. This is the first report that mycobacteria encode active and inactive forms of thioesterases, the latter of which appear to be unique to mycobacteria.