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Ribonuclease HepT-like This family includes the toxic component HepT of a type II toxin-antitoxin (TA) system, which has RNase activity. These proteins contain a HEPN (higher eukaryotes and prokaryotes nucleotide-binding) domain and are neutralized through tri-AMPylation by the cognate antitoxin MntA, containing a MNT (minimal nucleotidyltransferase) domain. HepT-MnA form an heterooctamer (at a 2:6 ratio), a rare organization for this kind of TA systems. HepT dimerizes and enables the formation of a deep cleft at the HEPN-domain interface, containing the RX4-6H motif (where X is any amino acid and the residue immediately after the conserved R is typically a polar amino acid) as the active site that functions as an RNA-cleaving RNase. This type II TA system regulates cell motility and confers plasmid stability. Due to the prevalence of these HEPN/MNT modules in bacteria and archaea, it has been suggested that these TA systems may also play a role in the environmental adaptation to extreme habitats. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",