鮑氏不動桿菌SK17乙醯化及丙醯化蛋白質體之研究

離胺酸乙醯化是一種廣泛分布於真核生物和細菌中的蛋白質轉譯後修飾。近來的研究發現，在真核生物中，許多乙醯化蛋白質於細胞各式各樣的反應中扮演著舉足輕重的角色，然而在原核細胞內，蛋白質乙醯化的功能和遍布範圍仍不明瞭。另外，離胺酸丙醯化是一個近年來新發現的離胺酸修飾，它被認為也對調控生物體的生理反應有著深遠的影響。本篇研究以質譜儀技術為基礎，並結合抗體免疫沉澱法進行蛋白質體學之分析，於醫院臨床菌株鮑氏不動桿菌SK17(Acinetobacter baumannii SK17)中檢測到174個乙醯化修飾位及96個丙醯化修飾位，分別來自於菌體中128個乙醯化蛋白質和71個丙醯化蛋白質。將這些乙醯化與丙醯化蛋白質體利用生物資訊學加以剖析後，我們發現這些蛋白質參與在多種不同的細胞反應中，包括核苷酸代謝、胺基酸代謝、醣類代謝、膜上運輸以及壓力反應。為了進一步確認這些轉譯後修飾對於蛋白質的影響，我們利用同源結構模擬法進行更深入的探討。當中有一個名為DNA結合蛋白HU (DNA-binding protein HU or nucleoid-associated protein HU)的二元體蛋白質，已知為染色體構型的維持和各種DNA相關反應的調節中重要的一員。此蛋白胺基酸序列第十三號的離胺酸上被偵測到有乙醯化的修飾，並且我們更驗證了這個修飾反應會改變HU蛋白的四級結構，以及降低其DNA的結合能力。本篇證實離胺酸乙醯化和丙醯化廣泛存在於鮑氏不動桿菌SK17，且建立了一個實證這些離胺酸轉譯後修飾對於生化功能的影響之成功範本，供後續研究的進行。

關鍵字

離氨酸乙醯化；離氨酸丙醯化；鮑氏不動桿菌SK17 ； DNA結合蛋白HU-β

並列摘要

Lysine acetylation is one of the most prevalent post-translational modifications (PTMs) detected in both eukaryotes and bacteria. Recently, many acetylproteins have been reported to play pivotal roles in various cellular processes in eukaryotes. However, the function and extent of this modification in prokaryotic cells remain largely unexplored. Besides, another novel lysine modification, lysine propionylation, is potential to have important functions in the regulation of biological processes. In this study, by using a mass spectrometry-based proteomic approach in combination with immunoprecipitation, we identified 174/ 96 lysine acetylation/ propionylation sites from 128/ 71 acetyl-/ propionylproteins in clinical isolates of Acinetobacter baumannii SK17. The bioinformatics analysis of both acetylome and propionylome showed that the identified proteins were involved in diverse cellular functions including nucleotide metabolism, amino acid metabolism, carbohydrate metabolism, membrane transporter and stress response. To further characterize the definite effects of these PTMs on proteins, we examined the identification of lysine-modified peptides based on their homologous protein structures. Among these, DNA-binding protein HU (also known as nucleoid-associated protein HU), a small dimeric protein, playing a critical role in maintenance of chromosomal architecture and various DNA transactions, was acetylated on Lys-13. In addition, we further proved this acetylated site would influence the stability of quaternary structure of HU protein and decrease its DNA binding ability. Our findings demonstrated that lysine acetylation and propinylation are abundant in A. baumannii SK17 and provide an in-depth exploration of the biological functions on lysine acetylated and propionylated proteins.

並列關鍵字

lysine acetylation ； lysine propionylation ； A. baumannii SK17 ； DNA-binding protein HU-β

參考文獻

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鮑氏不動桿菌SK17乙醯化及丙醯化蛋白質體之研究

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