5yep
From Proteopedia
Crystal structure of SO_3166-SO_3165 from Shewanella oneidensis
Structural highlights
FunctionMNTA_SHEON Antitoxin component of a type VII toxin-antitoxin (TA) system. Upon overexpression in situ or in E.coli neutralizes the effect of cognate toxin HepT (PubMed:26112399, PubMed:29555683, PubMed:33045733). Neutralization is mostly due to tri-AMPylation of toxin by this enzyme. Successively tri-AMPylates HepT on 'Tyr-104' (PubMed:33045733). Binds its own promoter, probably repressing its expression. The TA system confers plasmid stability in E.coli (PubMed:26112399).[1] [2] [3] Publication Abstract from PubMedToxin-antitoxin (TA) loci in bacteria are small genetic modules that regulate various cellular activities, including cell growth and death. The two-gene module encoding a HEPN (higher eukaryotes and prokaryotes nucleotide-binding) domain and a cognate MNT (minimal nucleotidyltransferase) domain have been predicted to represent a novel type II TA system prevalent in archaea and bacteria. However, the neutralization mechanism and cellular targets of the TA family remain unclear. The toxin SO_3166 having a HEPN domain and its cognate antitoxin SO_3165 with an MNT domain constitute a typical type II TA system that regulates cell motility and confers plasmid stability in the bacterium Shewanella oneidensis Here, we report the crystal structure and solution conformation of the SO_3166-SO_3165 pair, representing the first complex structures in this TA family. The structures revealed that SO_3165 and SO_3166 form a tight heterooctamer (at a 2:6 ratio), an organization that is very rare in other TA systems. We also observed that SO_3166 dimerization enables the formation of a deep cleft at the HEPN-domain interface harboring a composite RX4-6H active site that functions as an RNA-cleaving RNase. SO_3165 bound SO_3166 mainly through its two alpha-helices (alpha2 and alpha4), functioning as molecular recognition elements. Moreover, their insertion into the SO_3166 cleft sterically blocked the RX4-6H site or narrowed the cleft to inhibit RNA substrate binding. Structure-based mutagenesis confirmed the important roles of these alpha-helices in SO_3166 binding and inhibition. Our structure-function analysis provides first insights into the neutralization mechanism of the HEPN-MNT TA family. Structure-function analyses reveal the molecular architecture and neutralization mechanism of a bacterial HEPN-MNT toxin-antitoxin system.,Jia X, Yao J, Gao Z, Liu G, Dong YH, Wang X, Zhang H J Biol Chem. 2018 May 4;293(18):6812-6823. doi: 10.1074/jbc.RA118.002421. Epub, 2018 Mar 19. PMID:29555683[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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