Thermococcus gammatolerans EJ3 is an extremophile archaeon which was revealed as one of the most radioresistant organisms known on Earth, withstanding up to 30 kGy gamma-ray radiations. While its theoretical proteome is rather small, T. gammatolerans may enhance its toolbox by post-translational modification of its proteins. Here, we explored its extent of Nε-acetylation of lysines. For this, we immunopurified with two acetylated-lysine antibodies the acetylated peptides resulting from a proteolysis of soluble proteins with trypsin. The comparison of acetylated proteomes of two archaea highlights some common acetylation patterns but only 4 out of 26 orthologous proteins found to be acetylated in both species, are acetylated on the same lysine site. We evidenced that histone B is acetylated in T. gammatolerans at least at two different sites (K27 and K36), and a peptide common at the C-terminus of histones A and B is also acetylated. We verified that acetylation of histones is a common trait among Thermococcales after recording data on Thermococcus kodakaraensis histones and identifying three acetylated sites. This discovery reinforces the strong evolutionary link between Archaea and Eukaryotes and should be an incentive for further investigation on the extent and role of acetylation of histones in Archaea.

Significance

Acetylation is an important post-translational modification of proteins that has been extensively described in Eukaryotes, and more recently in Bacteria. Here, we report for the first time ever that histones in Archaea are also modified by acetylation after a systematic survey of acetylated peptides in Thermococcus gammatolerans. Structural models of histones A and B indicates that acetylation of the identified modified residues may play an important role in histone assembly and/or interaction with DNA. The in-depth protein acetylome landscape in T. gammatolerans includes at least 181 unique protein sequences, some of them being modified on numerous residues. Proteins involved in metabolic processes, information storage and processing mechanisms are over-represented categories in this dataset, highlighting the ancient role of this protein post-translational modification in primitive cells.

中文翻译：

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来自古细菌Thermococcus gammatolerans的赖氨酸特异性乙酰化蛋白质组揭示了乙酰化组蛋白的存在

嗜热热球菌EJ3是一种极端嗜热古生菌，被揭示为地球上已知的最耐辐射的生物之一，可承受高达30 kGy的伽玛射线辐射。尽管其理论蛋白质组相当小，但γ耐受性衣原体可能通过翻译后修饰其蛋白质来增强其工具箱。在这里，我们探讨了赖氨酸的Nε-乙酰化程度。为此，我们用两种乙酰化赖氨酸抗体免疫纯化了由可溶性蛋白与胰蛋白酶水解产生的乙酰化肽。两种古细菌的乙酰化蛋白质组的比较突出了一些常见的乙酰化模式，但是在两个物种中发现被乙酰化的26种直系同源蛋白质中，只有4种在相同的赖氨酸位点被乙酰化。我们证明了组蛋白B在至少在两个不同位点（K27和K36）的T. gammatolerans以及在组蛋白A和B的C-末端共有的肽也被乙酰化。我们证实组蛋白乙酰化是其中一个共同的特点Thermococcales上记录数据后，嗜热kodakaraensis组蛋白和确定了三个乙酰化网站。这一发现加强了古细菌与真核生物之间的牢固的进化联系，应成为进一步研究组蛋白乙酰化在古细菌中的程度和作用的诱因。

意义

乙酰化是蛋白质的重要​​的翻译后修饰，已在真核生物中和最近在细菌中广泛描述。在这里，我们有史以来第一次报道古细菌嗜热链球菌中乙酰化肽的系统调查后，古细菌中的组蛋白也被乙酰化修饰。组蛋白A和B的结构模型表明，已鉴定的修饰残基的乙酰化可能在组蛋白组装和/或与DNA的相互作用中起重要作用。γ耐受性的深入蛋白质乙酰基体景观。包括至少181个独特的蛋白质序列，其中一些在许多残基上进行了修饰。涉及代谢过程，信息存储和加工机制的蛋白质在该数据集中过分代表，说明了该蛋白质翻译后修饰在原始细胞中的古老作用。