Solution structure of Urm1 from Trypanosoma brucei
Solution structure of Urm1 from Trypanosoma brucei
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DOI：
10.1002/prot.22371
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发表时间：
2009-05
期刊：
影响因子：
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通讯作者：
Wen Zhang;Jiahai Zhang;Chao Xu;Tao Wang;Xuecheng Zhang;X. Tu
中科院分区：
文献类型：
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作者：
Wen Zhang;Jiahai Zhang;Chao Xu;Tao Wang;Xuecheng Zhang;X. Tu
泛素样蛋白修饰剂（ubitin -like protein modifiers, Ubls）参与多种生物过程并调节靶蛋白的活性和功能。当它们被偶联到靶蛋白上时，它们要么作为翻译后调节剂，要么作为靶蛋白降解的标记，通过包括激活酶、偶联酶和连接酶在内的酶级联反应许多Ubls已在真核生物中被发现然而，在原核生物中没有检测到蛋白质修饰剂。蛋白质修饰剂的进化过程仍然是一个谜。Urm1（泛素相关修饰物1，PF09138）属于Ubls家族。发现它与Urm1偶联途径中的e1样酶Uba4形成硫酯在酿酒酵母中，Urm1在氧化应激反应、营养生长中的出芽、单倍体状态下的琼脂侵入生长、二倍体状态下的假菌丝生长和饥饿条件下的细胞伸长等方面起着重要作用同时，测定了酵母中Urm1的溶液结构。通过结构比较发现，Urm1与钼钼合酶小亚基（MoaD）和硫胺生物合成相关的ThiS具有相似的结构在大肠杆菌中，MoaD和ThiS是两种硫载体蛋白，它们以依赖atp的方式被硫转移酶MoaB和thif激活8,9其机制类似于泛素激活酶e1.10,11对泛素的激活。此外，泛素、MoaD和ThiS都具有常规的b-抓褶。这些证据表明MoaD和ThiS可能是泛素的原核同源物。酵母Urm1与MoaD和ThiS的结构比较，结合泛素超家族的系统发育分析，表明Urm1可能是连接真核生物中atp依赖蛋白结合和atp依赖辅助因子硫化之间进化过程的独特“分子化石”布鲁氏锥虫是最古老的真核生物，具有许多独特的生物学特征。它在撒哈拉以南非洲引起人类和牛的昏睡病。15虽然它属于布鲁氏杆菌家族，但TbUrm1（布鲁氏T.中的Urm1）与人类的泛素序列只有11%的同源性。本文采用核磁共振法测定了TbUrm1的溶液结构。它具有泛素超家族典型的b-fold结构。结构比较发现，TbUrm1与酿酒酵母的Urm1和大肠杆菌的MoaD结构最为相似。这些结果进一步证实了Urm1在泛素超家族进化史中的重要作用。
Ubiquitin-like protein modifiers (Ubls) are involved in diverse biological processes and regulate the activity and function of target proteins. When they are conjugated to target proteins, they are either as a regulatory post-translational modifier, or tag for target protein degradation in the proteosome by an enzymatic cascade involving an activating enzyme, a conjugating enzyme, and a ligase.1,2 Many Ubls have been detected in eukaryotes.3 However, no protein modifier has been detected in prokaryotes. The evolutionary progress of protein modifier remains a puzzle. Urm1 (ubiquitin-related modifier 1, PF09138) belongs to Ubls family. It was found to form a thioester with Uba4, the E1-like enzyme in the Urm1 conjugation pathway.4 Urm1 plays a few important roles, including oxidant-stress response, budding in vegetative growth, invasive growth into agar in the haploid state, pseudohyphal growth, and cell elongation under starvation conditions in the diploid state in Saccharomyces cerevisiae.5,6 Meanwhile, the solution structure of Urm1 from yeast has been determined. Structural comparison reveals that Urm1 has the similar structure with MoaD (molybdopterin synthase small subunit) and ThiS (involved in thiamin biosynthesis).7 In Escherichia coli, MoaD and ThiS are two sulfur carrier proteins that are activated in an ATP-dependent manner by sulfur transferase, MoaB, and ThiF.8,9 The mechanism is similar to the activation of ubiquitin by the ubiquitin-activating enzyme E1.10,11 Additionally, ubiquitin, MoaD, and ThiS all have conventional b-grasp fold. These accumulated evidences imply that MoaD and ThiS might be prokaryotic homologs of ubiquitin.12–14 Structural comparison of yeast Urm1 and MoaD and ThiS, combining phylogenetic analysis of the ubiquitin superfamily, suggests that Urm1 might act as a unique ‘‘molecular fossil’’ connecting evolutionary course between ATP-dependent protein conjunction in eukaryotes and ATP-dependent cofactor sulfuration.7 Trypanosoma brucei is the most ancient and evolutionarily divergent eukaryote with many unique biological features. It causes sleeping sickness in human and nagana in cattle in sub-Saharan Africa.15 Although it belongs to Ubls family, TbUrm1 (Urm1 in T. brucei) has only 11% sequence identity with ubiquitin from human. In this article, the solution structure of TbUrm1 is determined by NMR. It shares the typical b-fold structure of ubiquitin superfamily. Structural comparison reveals that TbUrm1 has the most similar structure with Urm1 from Saccharomyces cerevisiae and MoaD from Escherichia coli. These results further confirm an important role of Urm1 in the evolutionary history of ubiquitin superfamily.