Crystal structure of hexanoyl-CoA bound to β-ketoacyl reductase FabG4 of Mycobacterium tuberculosis
Crystal structure of hexanoyl-CoA bound to β-ketoacyl reductase FabG4 of Mycobacterium tuberculosis
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DOI：
10.1042/bj20121107
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发表时间：
2013-02-15
影响因子：
4.1
通讯作者：
Das, Amit Kumar
中科院分区：
文献类型：
--
作者：
Dutta, Debajyoti;Bhattacharyya, Sudipta;Das, Amit Kumar
Fab G或β-氧代酰基还原酶参与脂肪酸合成。该反应需要NADPH/NADH介导的β-氧代酰基-ACP（酰基载体蛋白）转化为β-羟酰基-ACP。HMwFabG（高分子量FabG）形成一组遗传学上独立的FabG酶。FabG 4是来自结核分枝杆菌的HMwFabG，包含两个不同的结构域，N-末端“黄素氧还蛋白型”结构域和C-末端氧化还原酶结构域。催化活性C-末端结构域利用NADH将β-氧代酰基-CoA还原为β-羟酰基-CoA。在本研究中，已经确定了FabG 4 NADH二元复合物和FabG 4-NAD（+）-己酰-CoA三元复合物的晶体结构，以了解FabG 4的底物特异性和催化机制。这是第一份报告，以证明如何FabG 4相互作用，其辅酶NADH和己酰辅酶A，模拟延长脂肪酰链共价连接辅酶A。结构分析表明，在FabG的活性位点空腔内的己酰辅酶A的结合显著不同于与分枝杆菌FabI [InhA（烯酰-ACP还原酶）]结合的C-16脂肪酰底物的结合。三元复合物表明，环I和环II与CoA或ACP的磷酸泛酰巯基乙胺部分相互作用，以使共价连接的脂肪酰底物在活性位点附近对齐。结构数据ACP抑制研究表明FabG 4可以接受基于CoA和ACP的脂肪酰底物。我们还发现，在FabG 4二聚体中，一个单体的Arg（146）和Arg（445）与第二个单体的C-末端相互作用，在底物缔合和催化中起关键作用。
Fab Gs, or beta-oxoacyl reductases, are involved in fatty acid synthesis. The reaction entails NADPH/NADH-mediated conversion of beta-oxoacyl-ACP (acyl-carrier protein) into beta-hydroxyacyl-ACP. HMwFabGs (high-molecular-weight FabG) form a phylogenetically separate group of FabG enzymes. FabG4, an HMwFabG from Mycobacteriuni tuberculosis, contains two distinct domains, an N-terminal 'flavodoxintype' domain and a C-terminal oxoreductase domain. The catalytically active C-terminal domain utilizes NADH to reduce beta-oxoacyl-CoA to beta-hydroxyacyl-CoA. In the present study the crystal structures of the FabG4 NADH binary complex and the FabG4-NAD(+) -hexanoyl-CoA ternary complex have been determined to understand the substrate specificity and catalytic mechanism of FabG4. This is the first report to demonstrate how FabG4 interacts with its coenzyme NADH and hexanoyl-CoA that mimics an elongating fattyacyl chain covalently linked with CoA. Structural analysis shows that the binding of hexanoyl-CoA within the active site cavity of FabG significantly differs from that of the C-16 fattyacyl substrate bound to mycobacterial FabI [InhA (enoyl-ACP reductase)]. The ternary complex reveals that both loop I and loop II interact with the phosphopantetheine moiety of CoA or ACP to align the covalently linked fattyacyl substrate near the active site. Structural data ACP inhibition studies indicate that FabG4 can accept both CoA- and ACP-based fattyacyl substrates. We have also shown that in the FabG4 dimer Arg(146) and Arg(445) of one monomer interact with the C-terminus of the second monomer to play pivotal role in substrate association and catalysis.