PDF(Pubmed)
Abstract：
Ubiquitin-like proteins (Ubls) in eukaryotes and bacteria mediate sulfur transfer for the biosynthesis of sulfur-containing biomolecules and form conjugates with specific protein targets to regulate their functions. Here, we investigated the functions and physiological importance of Ubls in a hyperthermophilic archaeon by constructing a series of deletion mutants. We found that the Ubls (TK1065, TK1093, and TK2118) in Thermococcus kodakarensis are conjugated to their specific target proteins, and all three are involved in varying degrees in the biosynthesis of sulfur-containing biomolecules such as tungsten cofactor (Wco) and tRNA thiouridines. TK2118 (named UblB) is involved in the biosynthesis of Wco in a glyceraldehyde 3-phosphate:ferredoxin oxidoreductase, which is required for glycolytic growth, whereas TK1093 (named UblA) plays a key role in the efficient thiolation of tRNAs, which contributes to cellular thermotolerance. Intriguingly, in the presence of elemental sulfur (S0) in the culture medium, defective synthesis of these sulfur-containing molecules in Ubl mutants was restored, indicating that T. kodakarensis can use S0 as an alternative sulfur source without Ubls. Our analysis indicates that the Ubl-mediated sulfur-transfer system in T. kodakarensis is important for efficient sulfur assimilation, especially under low S0 conditions, which may allow this organism to survive in a low sulfur environment.IMPORTANCESulfur is a crucial element in living organisms, occurring in various sulfur-containing biomolecules including iron-sulfur clusters, vitamins, and RNA thionucleosides, as well as the amino acids cysteine and methionine. In archaea, the biosynthesis routes and sulfur donors of sulfur-containing biomolecules are largely unknown. Here, we explored the functions of Ubls in the deep-blanched hyperthermophilic archaeon, Thermococcus kodakarensis. We demonstrated functional redundancy of these proteins in the biosynthesis of tungsten cofactor and tRNA thiouridines and the significance of these sulfur-carrier functions, especially in low sulfur environments. We propose that acquisition of a Ubl sulfur-transfer system, in addition to an ancient inorganic sulfur assimilation pathway, enabled the primordial archaeon to advance into lower-sulfur environments and expand their habitable zone.
摘要：
真核生物和细菌中的泛素样蛋白（Ubls）介导硫转移，用于含硫生物分子的生物合成，并与特定的蛋白质靶标形成缀合物以调节其功能。这里,我们通过构建一系列缺失突变体，研究了超嗜热古细菌中Ubls的功能和生理重要性。我们发现柯达热球菌中的Ubls（TK1065，TK1093和TK2118）与其特定的靶蛋白缀合，这三者都在不同程度上参与了含硫生物分子如钨辅因子(Wco)和tRNA硫尿苷的生物合成。TK2118（命名为UblB）参与3-磷酸甘油醛中Wco的生物合成：铁氧还蛋白氧化还原酶，这是糖酵解生长所必需的，而TK1093（命名为UblA）在tRNA的有效巯基化中起着关键作用，这有助于细胞的耐热性。有趣的是，在培养基中存在元素硫（S0）的情况下，这些含硫分子在Ubl突变体中的合成缺陷得以恢复，表明柯达红藻可以使用S0作为没有Ubls的替代硫源。我们的分析表明，乌伯尔介导的硫转移系统是重要的有效的硫同化，特别是在低S0条件下，这可能会让这种生物在低硫环境中生存。重要的是硫是生物体中的关键元素，存在于各种含硫生物分子中，包括铁硫簇，维生素,和RNA硫代核苷，以及氨基酸半胱氨酸和蛋氨酸。在古细菌中,含硫生物分子的生物合成途径和硫供体在很大程度上是未知的。这里,我们探索了Ubls在深烫的超嗜热古细菌中的功能，柯达红球菌。我们证明了这些蛋白质在钨辅因子和tRNA硫尿苷的生物合成中的功能冗余以及这些硫载体功能的重要性，尤其是在低硫环境中。我们建议收购乌伯尔硫转移系统，除了古老的无机硫同化途径，使原始古细菌能够进入低硫环境并扩大其可居住区。
