Crystal structure of a substrate complex of Mycobacterium tuberculosis beta-ketoacyl-acyl carrier protein synthase III (FabH) with lauroyl-coenzyme A.
Crystal structure of a substrate complex of Mycobacterium tuberculosis beta-ketoacyl-acyl carrier protein synthase III (FabH) with lauroyl-coenzyme A.
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DOI：
10.1016/j.jmb.2004.12.044
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发表时间：
2005-03
影响因子：
5.6
通讯作者：
F. Musayev;S. Sachdeva;J. Scarsdale;K. A. Reynolds;H. Wright
中科院分区：
文献类型：
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作者：
F. Musayev;S. Sachdeva;J. Scarsdale;K. A. Reynolds;H. Wright
β-酮酰基-酰基载体蛋白合酶 III (FabH) 催化两步反应，启动植物和细菌中脂肪酸生物合成途径。在结核分枝杆菌中，FabH 催化月桂酰基、肉豆蔻酰基和棕榈酰基的延伸，由此形成细菌的细胞壁分枝菌酸。反应的第一步是酰基从酰基辅酶 A 转移到酶的活性位点半胱氨酸；第二步是通过与丙二酰基载体蛋白的克莱森缩合将酰基链延伸两个碳原子。我们之前已经确定了 II 型解离结核分枝杆菌 FabH 的晶体结构，它催化月桂酰基、肉豆蔻酰基和棕榈酰基的延伸。在这里，我们描述了 FabH 的第一个长链米氏底物复合物，即月桂酰辅酶 A 与结核分枝杆菌 FabH 催化失效的 Cys→Ala 突变体的复合物。从突变的活性位点半胱氨酸延伸的细长通道定义了酰基结合位点，该位点赋予结核分枝杆菌 FabH 独特的酰基底物特异性。 CoA 位于第二个通道中，主要通过其在酶表面的核苷酸基团的相互作用而结合。该复合物中辅酶 A 的明显弱缔合可能在长链酰基辅酶 A 底物和产物的结合和解离中发挥作用，并提出了与该酶的机制相关的问题。
β-Ketoacyl-acyl carrier protein synthase III (FabH) catalyzes a two step reaction that initiates the pathway of fatty acid biosynthesis in plants and bacteria. In Mycobacterium tuberculosis, FabH catalyzes extension of lauroyl, myristoyl and palmitoyl groups from which cell wall mycolic acids of the bacterium are formed. The first step of the reaction is an acyl group transfer from acyl-coenzyme A to the active-site cysteine of the enzyme; the second step is acyl chain extension by two carbon atoms through Claisen condensation with malonyl-acyl carrier protein. We have previously determined the crystal structure of a type II, dissociated M.tuberculosis FabH, which catalyzes extension of lauroyl, myristoyl and palmitoyl groups. Here we describe the first long-chain Michaelis substrate complex of a FabH, that of lauroyl-coenzyme A with a catalytically disabled Cys→Ala mutant of M.tuberculosis FabH. An elongated channel extending from the mutated active-site cysteine defines the acyl group binding locus that confers unique acyl substrate specificity on M.tuberculosis FabH. CoA lies in a second channel, bound primarily through interactions of its nucleotide group at the enzyme surface. The apparent weak association of CoA in this complex may play a role in the binding and dissociation of long chain acyl-CoA substrates and products and poses questions pertinent to the mechanism of this enzyme.