Structural analysis of Shigella flexneri bi-functional enzyme HisIE in histidine biosynthesis
Structural analysis of Shigella flexneri bi-functional enzyme HisIE in histidine biosynthesis
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福氏志贺菌组氨酸生物合成双功能酶HisIE的结构分析
DOI：
10.1016/j.bbrc.2019.06.099
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发表时间：
2019
影响因子：
3.1
通讯作者：
Zhang Heqiao
中科院分区：
文献类型：
--
作者：
Wang Yannan;Zhang Fan;Nie Yan;Shang Guijun;Zhang Heqiao
组氨酸的生物合成在动物中是不存在的，但在革兰氏阴性细菌中被证明是高度保守的，因此使其成为抗生素设计的一个有吸引力的目标。组氨酸生物合成途径中的酶有多种融合形式，由于缺乏结构信息，人们对其结构域组织和催化机制的了解还很有限。在这里，我们报道了志贺氏菌福氏双功能酶HisIE(SfHisIE)的第一个晶体结构，它在组氨酸生物合成途径的第二步和第三步发挥作用。这种结构表明HisIE以二聚体的形式存在，在N端和C端分别连接Hise和Hisi的两个二聚体(融合环)。我们的突变研究表明，这个融合环中的突变对细菌是致命的，这表明基因融合在组氨酸生物合成中的优势。结构分析显示，在Hise和Hisi的配体结合沟中存在几个高度保守的残基，表明革兰氏阴性菌之间存在进化上保守的催化机制。
Histidine biosynthesis, which is absent in animals, was shown to be highly conserved among gram-negative bacteria, thus making it an attractive target for antibiotic design. There are many fusion forms of enzymes in the histidine biosynthetic pathway and people still have limited knowledge about their domain organizations and catalytic mechanisms, due to the lack of structural information. Here we report the first crystal structure ofShigella flexneribi-functional enzyme HisIE (SfHisIE) that functions in the 2nd and 3rd steps in the histidine biosynthetic pathway. This structure shows that HisIE exists as dimers with two loops (fusion loop) connecting the individual dimer of HisE and HisI in its N-terminus and C-terminus respectively. Our mutagenesis study shows mutations in this fusion loop are lethal for bacteria indicating the advantage of gene fusion in Histidine biosynthesis. Structural analysis revealed several highly conserved residues in the putative ligand binding grooves of HisE and HisI, showing an evolutionarily conserved catalytic mechanism shared among gram negative-bacteria.