Structural basis for catalysis of a tetrameric class IIa fructose 1,6-bisphosphate aldolase from Mycobacterium tuberculosis.
Structural basis for catalysis of a tetrameric class IIa fructose 1,6-bisphosphate aldolase from Mycobacterium tuberculosis.
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DOI：
10.1016/j.jmb.2009.01.003
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发表时间：
2009-03-06
影响因子：
5.6
通讯作者：
Mesecar, Andrew D.
中科院分区：
文献类型：
--
作者：
Pegan, Scott D.;Rukseree, Kamolchanok;Franzblau, Scott G.;Mesecar, Andrew D.
关键词：
结核分枝杆菌是结核病(TB)的病原体，目前以潜伏形式感染着世界三分之一的人口。耐多药结核和广泛耐药结核菌株的出现突显了在结核分枝杆菌中建立新的药理靶点的必要性。结核分枝杆菌IIa类果糖1，6-二磷酸缩醛酶(MtFBA)由于在潜伏性结核病中表达上调，已被认为是此类靶点之一。由于MtFBA的结构尚未确定，而且关于其反应机理的信息很少，因此我们试图确定MtFBA与其底物形成的络合物的X射线结构。通过降低结晶状态下酶的pH，我们能够确定二羟基丙酮磷酸(DHAP)、3-磷酸甘油醛(G3P)和1，6-二磷酸果糖(FBP)分别在1.5、2.1和1.3奥处与MtFBA结合的一系列高分辨X射线结构。通过这些结构，我们发现MtFBA属于一种新的IIa型四聚体。四聚体界面的分子细节揭示了能够更好地根据FFA的一级序列预测其四元结构的重要信息。这些X射线结构还提供了有趣的和新的细节，以了解第二类FBAs的反应机理。不仅观察到底物和产物的几何构型准备催化，而且出人意料的是，DHAP的羟基烯醇酸中间体也被捕获并在结构上拆分。这些简明的新细节使人们更好地了解了FBAs的反应机理，并为针对这类酶的抑制剂设计工作提供了结构基础。
Mycobacterium tuberculosis, the causative agent of tuberculosis (TB), currently infects one third of the world’s population in its latent form. The emergence of multidrug resistant strains, MDR-TB and XDR-TB has highlighted the need for new pharmacological targets within M. tuberculosis. The Class IIa fructose 1,6-bisphosphate aldolase (FBA) enzyme from M. tuberculosis (MtFBA) has been proposed as one such target since its upregulated in latent TB. Since the structure of MtFBA had not been determined and since there was little information available on its reaction mechanism, we sought to determine the X-ray structure of MtFBA in complex with its substrates. By lowering the pH of the enzyme in the crystalline state, we were able to determine a series of high-resolution X-ray structures of MtFBA bound to dihydroxyacetonephosphate (DHAP), glyceraldehyde-3-phosphate (G3P), and fructose 1,6-bisphosphate (FBP) at 1.5 Å, 2.1 Å, and 1.3 Å respectively. Through these structures it was discovered that MtFBA belongs to a novel tetrameric class of the type IIa FBAs. The molecular details at the interface of the tetramer revealed important information for being able to better predict the quaternary structures among the FBAs based on their primary sequences. These X-ray structures also provide interesting and new details on the reaction mechanism of class II FBAs. Not only were the substrates and products observed in geometries poised for catalysis, but unexpectedly the hydroxyl enolate intermediate of DHAP was also captured and resolved structurally. These concise new details provide a better understanding of the reaction mechanisms for FBAs in general and provide a structural basis for inhibitor design efforts aimed at this class of enzymes.
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