In all domains of life, ribonucleic acid (RNA) maturation includes post-transcriptional chemical modifications of nucleosides. Many sulfur-containing nucleosides have been identified in transfer RNAs (tRNAs), such as the derivatives of 2-thiouridine (s²U), 4-thiouridine (s⁴U), 2-thiocytidine (s²C), 2-methylthioadenosine (ms²A). These modifications are essential for accurate and efficient translation of the genetic code from messenger RNA (mRNA) for protein synthesis. This review summarizes the recent discoveries concerning the mechanistic and structural characterization of tRNA thiolation enzymes that catalyze the non-redox substitution of oxygen for sulfur in nucleosides. Two mechanisms have been described. One involves persulfide formation on catalytic cysteines, while the other uses a [4Fe–4S] cluster, chelated by three conserved cysteines only, as a sulfur carrier.

在生命的所有领域，核糖核酸 (RNA) 的成熟包括核苷的转录后化学修饰。在转移 RNA (tRNA) 中已鉴定出许多含硫核苷，例如 2-硫尿苷 (s ² U)、4-硫尿苷 (s ⁴ U)、2-硫胞苷 (s ² C)、2-甲基硫腺苷的衍生物（毫秒²一种）。这些修饰对于从信使 RNA (mRNA) 准确有效地翻译用于蛋白质合成的遗传密码至关重要。这篇综述总结了最近关于 tRNA 硫醇化酶的机制和结构特征的发现，这些酶催化核苷中氧的非氧化还原取代。已经描述了两种机制。一个涉及在催化半胱氨酸上形成过硫化物，而另一个使用 [4Fe-4S] 簇，仅由三个保守的半胱氨酸螯合，作为硫载体。