Structural basis of ubiquitination mediated by protein splicing in early Eukarya.
BIL2-X-ray structure
BIL2-intein
BUBL locus
GTPase K-Ras ubiquitination
Protein splicing
Journal
Biochimica et biophysica acta. General subjects
ISSN: 1872-8006
Titre abrégé: Biochim Biophys Acta Gen Subj
Pays: Netherlands
ID NLM: 101731726
Informations de publication
Date de publication:
05 2021
05 2021
Historique:
received:
12
10
2020
revised:
28
12
2020
accepted:
08
01
2021
pubmed:
15
1
2021
medline:
30
6
2021
entrez:
14
1
2021
Statut:
ppublish
Résumé
Inteins are intervening proteins, which are known to perform protein splicing. The reaction results in the production of an intein domain and an inteinless protein, which shows no trace of the insertion. BIL2 is part of the polyubiquitin locus of Tetrahymena thermophila (BUBL), where two bacterial-intein-like (BIL) domains lacking the C + 1 nucleophile, are flanked by two independent ubiquitin-like domains (ubl4/ubl5). We solved the X-ray structures of BIL2 in both the inactive and unprecedented, zinc-induced active, forms. Then, we characterized by mass spectrometry the BUBL splicing products in the absence and in the presence of T.thRas-GTPase. Finally, we investigated the effect of ubiquitination on T.thRas-GTPase by molecular dynamics simulations. The structural analysis demonstrated that zinc-induced conformational change activates protein splicing. Moreover, mass spectrometry characterization of the splicing products shed light on the possible function of BIL2, which operates as a "single-ubiquitin-dispensing-platform", allowing the conjugation, via isopeptide bond formation (K(εNH We demonstrated that BIL2 is activated by zinc and that protein splicing induced by this intein does not take place through classical or aminolysis mechanisms but via formation of a covalent isopeptide bond, causing the ubiquitination of endogenous substrates such as T.thRas-GTPase. In this "enzyme-free" ubiquitination mechanism the isopeptide formation, which canonically requires E1-E2-E3 enzymatic cascade and constitutes the alphabet of ubiquitin biology, is achieved in a single, concerted step without energy consumption.
Sections du résumé
BACKGROUND
Inteins are intervening proteins, which are known to perform protein splicing. The reaction results in the production of an intein domain and an inteinless protein, which shows no trace of the insertion. BIL2 is part of the polyubiquitin locus of Tetrahymena thermophila (BUBL), where two bacterial-intein-like (BIL) domains lacking the C + 1 nucleophile, are flanked by two independent ubiquitin-like domains (ubl4/ubl5).
METHODS
We solved the X-ray structures of BIL2 in both the inactive and unprecedented, zinc-induced active, forms. Then, we characterized by mass spectrometry the BUBL splicing products in the absence and in the presence of T.thRas-GTPase. Finally, we investigated the effect of ubiquitination on T.thRas-GTPase by molecular dynamics simulations.
RESULTS
The structural analysis demonstrated that zinc-induced conformational change activates protein splicing. Moreover, mass spectrometry characterization of the splicing products shed light on the possible function of BIL2, which operates as a "single-ubiquitin-dispensing-platform", allowing the conjugation, via isopeptide bond formation (K(εNH
CONCLUSIONS
We demonstrated that BIL2 is activated by zinc and that protein splicing induced by this intein does not take place through classical or aminolysis mechanisms but via formation of a covalent isopeptide bond, causing the ubiquitination of endogenous substrates such as T.thRas-GTPase.
GENERAL SIGNIFICANCE
In this "enzyme-free" ubiquitination mechanism the isopeptide formation, which canonically requires E1-E2-E3 enzymatic cascade and constitutes the alphabet of ubiquitin biology, is achieved in a single, concerted step without energy consumption.
Identifiants
pubmed: 33444728
pii: S0304-4165(21)00003-9
doi: 10.1016/j.bbagen.2021.129844
pii:
doi:
Substances chimiques
Polyubiquitin
120904-94-1
Zinc
J41CSQ7QDS
Types de publication
Journal Article
Research Support, Non-U.S. Gov't
Langues
eng
Sous-ensembles de citation
IM
Pagination
129844Informations de copyright
Copyright © 2021 Elsevier B.V. All rights reserved.