The structure of (3R)-hydroxyacyl-acyl carrier protein dehydratase (FabZ) from Pseudomonas aeruginosa
The structure of (3R)-hydroxyacyl-acyl carrier protein dehydratase (FabZ) from Pseudomonas aeruginosa
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DOI：
10.1074/jbc.m408105200
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发表时间：
2004-12-10
影响因子：
4.8
通讯作者：
Rock, CO
中科院分区：
文献类型：
--
作者：
Kimber, MS;Martin, F;Rock, CO
II型脂肪酸生物合成系统对细菌的膜形成至关重要，使该途径的组成蛋白成为抗菌药物发现的有吸引力的靶点。II型脂肪酸生物合成延伸周期的第三步由β -羟基酰基载体蛋白（ACP）脱水酶催化。有两种同工异构体。FabZ可以催化(3R)-羟基酰基- acp脱水为反式-2-酰基- acp，是细菌II型系统中普遍表达的成分。第二种异构体FabA在自然界的分布较为有限，除脱水外，还能将反式-2-异构化为顺式-3-十烯基- acp，这是不饱和脂肪酸生物合成的重要步骤。本文报道了人类重要病原体铜绿假单胞菌中FabZ蛋白在2.5埃分辨率下的结构。PaFabZ是一种六聚体（二聚体的三聚体），His/Glu催化二偶体位于二聚体界面形成的深而窄的隧道中。位点诱变实验表明，区分脱水酶的FabA和FabZ亚家族的活性位点残基的明显差异并不能解释FabA催化异构化的独特能力。由于这两种酶的催化机制实际上难以区分，因此观察到的FabA和FabZ的底物结合通道形状的结构差异使我们假设不同形状的通道控制了结合底物的构象和定位，从而使FabA而不是FabZ催化异构化反应。
Type II fatty acid biosynthesis systems are essential for membrane formation in bacteria, making the constituent proteins of this pathway attractive targets for antibacterial drug discovery. The third step in the elongation cycle of the type II fatty acid biosynthesis is catalyzed by beta-hydroxyacyl-(acyl carrier protein) (ACP) dehydratase. There are two isoforms. FabZ, which catalyzes the dehydration of (3R)-hydroxyacyl-ACP to trans-2-acyl-ACP, is a universally expressed component of the bacterial type II system. FabA, the second isoform, as has more limited distribution in nature and, in addition to dehydration, also carries out the isomerization of trans-2- to cis-3-decenoyl-ACP as an essential step in unsaturated fatty acid biosynthesis. We report the structure of FabZ from the important human pathogen Pseudomonas aeruginosa at 2.5 Angstrom of resolution. PaFabZ is a hexamer ( trimer of dimers) with the His/Glu catalytic dyad located within a deep, narrow tunnel formed at the dimer interface. Site-directed mutagenesis experiments showed that the obvious differences in the active site residues that distinguish the FabA and FabZ subfamilies of dehydratases do not account for the unique ability of FabA to catalyze isomerization. Because the catalytic machinery of the two enzymes is practically indistinguishable, the structural differences observed in the shape of the substrate binding channels of FabA and FabZ lead us to hypothesize that the different shapes of the tunnels control the conformation and positioning of the bound substrate, allowing FabA, but not FabZ, to catalyze the isomerization reaction.