Structural characterization and comparison of the large subunits of IPM isomerase and homoaconitase from Methanococcus jannaschii
Structural characterization and comparison of the large subunits of IPM isomerase and homoaconitase from Methanococcus jannaschii
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DOI：
10.1107/s1399004713033762
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发表时间：
2014-04-01
影响因子：
2.2
通讯作者：
Hwang, Kwang Yeon
中科院分区：
文献类型：
--
作者：
Lee, Eun Hye;Lee, Kitaik;Hwang, Kwang Yeon
乌头酸酶蛋白质家族包括三类氢裂解酶：乌头酸酶、高乌头酸酶和苹果酸异丙酯 (IPM) 异构酶。它们具有共同的 Fe-S 簇结合位点，并通过连续脱水和水合催化特定底物的异构化。古细菌詹氏甲烷球菌含有两种乌头酸酶家族蛋白：IPM 异构酶和高乌头酸酶，它们具有 50% 的序列同一性。这两种酶是异二聚体蛋白质，由不同基因编码的大小亚基组成。尽管已经报道了两种酶的小亚基的结构，但来自 M. jannaschii 的 IPM 异构酶大亚基（分别为 ox-MJ0499 和 red-MJ0499）的氧化和还原形式的第一个结构在此分别报道为 1.8 和 2.7 埃分辨率，以及高乌头酸酶大亚基（MJ1003）的结构为 2.5 埃。 埃分辨率。两种蛋白质的结构均具有未结合的 Fe-S 簇，并在活性位点包含第四个半胱氨酸。 MJ1003的活性位点与乌头酸酶的活性位点同源，而MJ0499与乌头酸酶相比，活性位点存在明显的结构扭曲。此外，与ox-MJ0499相比，在red-MJ0499的活性位点观察到显着的大构象变化。这两种蛋白质的活性位点在转变为乌头酸酶中观察到的 Fe-S 簇结合“激活”状态之前采用两种不同的状态。 MJ1003 有一个“开放”活性位点，形成簇的活性口袋，而 ox-MJ0499 有一个“封闭”活性位点，在二硫键中有四个半胱氨酸。这些数据将有助于理解Fe-S蛋白家族聚类的生化机制。
The aconitase family of proteins includes three classes of hydro-lyase enzymes: aconitases, homoaconitases and isopropylmalate (IPM) isomerases. They have a common Fe-S cluster-binding site and catalyze the isomerization of specific substrates by sequential dehydration and hydration. The archaeon Methanococcus jannaschii contains two aconitase family proteins, IPM isomerase and homoaconitase, which have 50% sequence identity. These two enzymes are heterodimeric proteins composed of large and small subunits encoded by separate genes. Although structures have been reported for the small subunits of the two enzymes, the first structures of oxidized and reduced forms of the large subunit of IPM isomerase (ox-MJ0499 and red-MJ0499, respectively) from M. jannaschii are reported here at 1.8 and 2.7 angstrom resolution, respectively, together with the structure of the large subunit of homoaconitase (MJ1003) at 2.5 angstrom resolution. The structures of both proteins have unbound Fe-S clusters and contain a fourth cysteine in the active site. The active site of MJ1003 is homologous to that of aconitase, whereas MJ0499 has significant structural distortion at the active site compared with aconitase. In addition, significant large conformational changes were observed in the active site of red-MJ0499 when compared with ox-MJ0499. The active sites of the two proteins adopt two different states before changing to the Fe-S cluster-bound 'activated' state observed in aconitase. MJ1003 has an 'open' active site, which forms an active pocket for the cluster, while ox-MJ0499 has a ` closed' active site, with four cysteines in disulfide bonds. These data will be helpful in understanding the biochemical mechanism of clustering of the Fe-S protein family.