期刊
MOLECULAR CELL
卷 80, 期 6, 页码 955-+出版社
CELL PRESS
DOI: 10.1016/j.molcel.2020.11.034
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资金
- Research Council of Lithuania [S-LJB-17-1]
- European Social Fund [09.3.3-LMT-K-712-01-0126, 09.3.3-LMT-K-712-01-0080]
- Research Council of Lithuania (LMTLT)
Prokaryotic toxin-antitoxin (TA) systems are composed of a toxin capable of interfering with key cellular processes and its neutralizing antidote, the antitoxin. Here, we focus on the HEPN-MNT TA system encoded in the vicinity of a subtype I-D CRISPR-Cas system in the cyanobacterium Aphanizomenon flos-aquae. We show that HEPN acts as a toxic RNase, which cleaves off 4 nt from the 3' end in a subset of tRNAs, thereby interfering with translation. Surprisingly, we find that the MNT (minimal nucleotidyltransferase) antitoxin inhibits HEPN RNase through covalent di-AMPylation (diadenylylation) of a conserved tyrosine residue, Y109, in the active site loop. Furthermore, we present crystallographic snapshots of the di-AMPylation reaction at different stages that explain the mechanism of HEPN RNase inactivation. Finally, we propose that the HEPN-MNT system functions as a cellular ATP sensor that monitors ATP homeostasis and, at low ATP levels, releases active HEPN toxin.
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