N-Terminal Modifications of Ubiquitin via Methionine Excision,Deamination, and Arginylation Expand the Ubiquitin Code |
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Authors: | Kha The Nguyen Shinyeong Ju Sang-Yoon Kim Chang-Seok Lee Cheolju Lee Cheol-Sang Hwang |
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Institution: | 1.Department of Life Sciences, Pohang University of Science and Technology, Pohang 37673, Korea;2.Center for Theragnosis, Korea Institute of Science and Technology, Seoul 02792, Korea;3.Division of Bio-Medical Science & Technology, KIST School, Korea University of Science and Technology, Seoul 02792, Korea |
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Abstract: | Ubiquitin (Ub) is post-translationally modified by Ub itself or Ub-like proteins, phosphorylation, and acetylation, among others, which elicits a variety of Ub topologies and cellular functions. However, N-terminal (Nt) modifications of Ub remain unknown, except the linear head-to-tail ubiquitylation via Nt-Met. Here, using the yeast Saccharomyces cerevisiae and an Nt-arginylated Ub-specific antibody, we found that the detectable level of Ub undergoes Nt-Met excision, Nt-deamination, and Nt-arginylation. The resulting Nt-arginylated Ub and its conjugated proteins are upregulated in the stationary-growth phase or by oxidative stress. We further proved the existence of Nt-arginylated Ub in vivo and identified Nt-arginylated Ub-protein conjugates using stable isotope labeling by amino acids in cell culture (SILAC)-based tandem mass spectrometry. In silico structural modeling of Nt-arginylated Ub predicted that Nt-Arg flexibly protrudes from the surface of the Ub, thereby most likely providing a docking site for the factors that recognize it. Collectively, these results reveal unprecedented Nt-arginylated Ub and the pathway by which it is produced, which greatly expands the known complexity of the Ub code. |
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Keywords: | arginylation deamination methionine excision N-degron proteolysis ubiquitin code |
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