4glk
From Proteopedia
Structure and activity of AbiQ, a lactococcal anti-phage endoribonuclease belonging to the type-III toxin-antitoxin system
Structural highlights
FunctionABIQ_LACLL Toxic component of a type III toxin-antitoxin (TA) system. An endoribonuclease that is probably sequence-specific. It is neutralized by its cognate antitoxin RNA AntiQ, which has 2.8 35 nucleotide-long repeats. Cannot be cloned in L.lactis subsp. cremoris strain NZ9000 in the absence of the antitoxin gene; expression in strain NZ9000 even in the presence of antiQ inhibits growth in a bacteriostatic fashion (PubMed:23279123). Confers resistance to 936 and c2 phages but not P335 phages in L.lactis, causes an abortive infection (Abi phenotype). Viral DNA is replicated but not cleaved from its concatemeric form, while the viral major structural protein is produced normally in the presence of this protein (PubMed:9835558). Operon expression in E.coli confers resistance to 3 phages of the Myoviridae family (T4, RB69 and phage 2) and 1 of the Siphoviridae family (T5), but not other tested phages (T1, T3, lambda vir, HK97, Mu and pilH alpha). The presence of this operon in L.lactis subsp. lactis strain IL1403 during phage P008 infection alters the viral transcription profiles (PubMed:23813728).[1] [2] [3] Publication Abstract from PubMedAbiQ is a phage resistance mechanism found on a native plasmid of Lactococcus lactis that abort virulent phage infections. In this study, we experimentally demonstrate that AbiQ belongs to the recently described type III toxin-antitoxin systems. When overexpressed, the AbiQ protein (ABIQ) is toxic and causes bacterial death in a bacteriostatic manner. Northern and Western blot experiments revealed that the abiQ gene is transcribed and translated constitutively, and its expression is not activated by a phage product. ABIQ is an endoribonuclease that specifically cleaves its cognate antitoxin RNA molecule in vivo. The crystal structure of ABIQ was solved and site-directed mutagenesis identified key amino acids for its anti-phage and/or its RNase function. The AbiQ system is the first lactococcal abortive infection system characterized to date at a structural level. Structure and activity of AbiQ, a lactococcal endoribonuclease belonging to the type III toxin-antitoxin system.,Samson JE, Spinelli S, Cambillau C, Moineau S Mol Microbiol. 2012 Dec 20. doi: 10.1111/mmi.12129. PMID:23279123[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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