title: Structure and activity of AbiQ, a lactococcal endoribonuclease belonging to the type III toxin-antitoxin system.
abstract: AbiQ 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.
authors.affiliation: Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et génie, Université Laval, Québec, Canada, G1V 0A6.
authors.forename: Julie E
authors.initials: JE
authors.lastname: Samson
authors.forename: Silvia
authors.initials: S
authors.lastname: Spinelli
authors.forename: Christian
authors.initials: C
authors.lastname: Cambillau
authors.forename: Sylvain
authors.initials: S
authors.lastname: Moineau
mesh_terms: D000595:Amino Acid Sequence; D000992:Antitoxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004722:Endoribonucleases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D013294:Lactococcus lactis / Q000737:chemistry / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism; D008958:Models, Molecular; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism
chemical_list: C116791:AbiQ protein, Lactococcus lactis; D000992:Antitoxins; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D012329:RNA, Bacterial; D004722:Endoribonucleases