Leidel Sebastian, Pedrioli Patrick G A, Bucher Tamara, Brost Renée, Costanzo Michael, Schmidt Alexander, Aebersold Ruedi, Boone Charles, Hofmann Kay, Peter Matthias
Institute of Biochemistry, ETH Zurich, Schafmattstrasse 18, CH-8093 Zurich, Switzerland.
Nature. 2009 Mar 12;458(7235):228-32. doi: 10.1038/nature07643. Epub 2009 Jan 14.
Ubiquitin-like proteins (UBLs) can change protein function, localization or turnover by covalent attachment to lysine residues. Although UBLs achieve this conjugation through an intricate enzymatic cascade, their bacterial counterparts MoaD and ThiS function as sulphur carrier proteins. Here we show that Urm1p, the most ancient UBL, acts as a sulphur carrier in the process of eukaryotic transfer RNA (tRNA) modification, providing a possible evolutionary link between UBL and sulphur transfer. Moreover, we identify Uba4p, Ncs2p, Ncs6p and Yor251cp as components of this conserved pathway. Using in vitro assays, we show that Ncs6p binds to tRNA, whereas Uba4p first adenylates and then directly transfers sulphur onto Urm1p. Finally, functional analysis reveals that the thiolation function of Urm1p is critical to regulate cellular responses to nutrient starvation and oxidative stress conditions, most likely by increasing translation fidelity.
类泛素蛋白（UBLs）可通过共价连接到赖氨酸残基来改变蛋白质的功能、定位或周转。尽管UBLs通过复杂的酶促级联反应实现这种缀合，但它们在细菌中的对应物MoaD和ThiS作为硫载体蛋白发挥作用。在这里，我们表明最古老的UBL——Urm1p，在真核生物转移RNA（tRNA）修饰过程中作为硫载体，为UBL与硫转移之间提供了可能的进化联系。此外，我们确定Uba4p、Ncs2p、Ncs6p和Yor251cp是这一保守途径的组成部分。通过体外实验，我们表明Ncs6p与tRNA结合，而Uba4p首先将腺苷酸化，然后直接将硫转移到Urm1p上。最后，功能分析表明，Urm1p的硫醇化功能对于调节细胞对营养饥饿和氧化应激条件的反应至关重要，最有可能是通过提高翻译保真度来实现的。
