IMR Press / FBL / Volume 17 / Issue 4 / DOI: 10.2741/3996

Frontiers in Bioscience-Landmark (FBL) is published by IMR Press from Volume 26 Issue 5 (2021). Previous articles were published by another publisher on a subscription basis, and they are hosted by IMR Press on as a courtesy and upon agreement with Frontiers in Bioscience.

Open Access Article
The natural history of ubiquitin and ubiquitin-related domains
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1 Omics Science Center (OSC), RIKEN Yokohama Institute, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama-shi, 230-0045 Kanagawa, Japan
2 National Center for Biotechnology Information, National Library of Medicine, National Institutes of Health, Bethesda, MD 20894, United States of America

Academic Editor: Mario Garcia-Dominguez

Front. Biosci. (Landmark Ed) 2012, 17(4), 1433–1460;
Published: 1 January 2012
(This article belongs to the Special Issue Ubiquitin-like proteins)

The ubiquitin (Ub) system is centered on conjugation and deconjugation of Ub and Ub-like (Ubls) proteins by a system of ligases and peptidases, respectively. Ub/Ubls contain the beta-grasp fold, also found in numerous proteins with biochemically distinct roles unrelated to the conventional Ub-system. The beta-GF underwent an early radiation spawning at least seven clades prior to the divergence of extant organisms from their last universal common ancestor, first emerging in the context of translation-related RNA-interactions and subsequently exploding to occupy various functional niches. Most beta-GF diversification occurred in prokaryotes, with the Ubl clade showing dramatic expansion in the eukaryotes. Diversification of Ubl families in eukaryotes played a major role in emergence of characteristic eukaryotic cellular sub-structures and systems. Recent comparative genomics studies indicate precursors of the eukaryotic Ub-system emerged in prokaryotes. The simplest of these combine an Ubl and an E1-like enzyme in metabolic pathways. Sampylation in archaea and Urmylation in eukaryotes appear to represent recruitment of such systems as simple protein-tagging apparatuses. However, other prokaryotic systems incorporated further components and mirror the eukaryotic condition in possessing an E2, a RING-type E3 or both of these components. Additionally, prokaryotes have evolved conjugation systems independent of Ub ligases, such as the Pup system.

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