PDF(Pubmed)
Abstract：
Post-translational modifications by ubiquitin-like proteins (UBLs) are essential for nearly all cellular processes. Ubiquitin-related modifier 1 (Urm1) is a unique UBL, which plays a key role in tRNA anticodon thiolation as a sulfur carrier protein (SCP) and is linked to the noncanonical E1 enzyme Uba4 (ubiquitin-like protein activator 4). While Urm1 has also been observed to conjugate to target proteins like other UBLs, the molecular mechanism of its attachment remains unknown. Here, we reconstitute the covalent attachment of thiocarboxylated Urm1 to various cellular target proteins in vitro, revealing that, unlike other known UBLs, this process is E2/E3-independent and requires oxidative stress. Furthermore, we present the crystal structures of the peroxiredoxin Ahp1 before and after the covalent attachment of Urm1. Surprisingly, we show that urmylation is accompanied by the transfer of sulfur to cysteine residues in the target proteins, also known as cysteine persulfidation. Our results illustrate the role of the Uba4-Urm1 system as a key evolutionary link between prokaryotic SCPs and the UBL modifications observed in modern eukaryotes.
摘要：
泛素样蛋白（UBL）的翻译后修饰对于几乎所有细胞过程都是必不可少的。泛素相关修饰符1(Urm1)是一种独特的UBL，作为硫载体蛋白（SCP）在tRNA反密码子硫醇化中起关键作用，并与非规范的E1酶Uba4（泛素样蛋白激活剂4）连接。虽然Urm1也被观察到与靶蛋白如其他UBL结合，其附着的分子机制仍然未知。这里,我们在体外重建硫代羧基化Urm1与各种细胞靶蛋白的共价连接，揭示了这一点，与其他已知的UBL不同，该过程不依赖E2/E3,需要氧化应激。此外，我们介绍了过氧化物氧还蛋白Ahp1在Urm1共价连接之前和之后的晶体结构。令人惊讶的是,我们表明，在靶蛋白中，尿嘧啶化伴随着硫向半胱氨酸残基的转移，也称为半胱氨酸过硫化。我们的结果说明了Uba4-Urm1系统作为原核SCPP与现代真核生物中观察到的UBL修饰之间的关键进化联系的作用。
