title: Mutational Analysis of the Antitoxin in the Lactococcal Type III Toxin-Antitoxin System AbiQ.
abstract: The lactococcal abortive phage infection mechanism AbiQ recently was classified as a type III toxin-antitoxin system in which the toxic protein (ABIQ) is regulated following cleavage of its repeated noncoding RNA antitoxin (antiQ). In this study, we investigated the role of the antitoxin in antiphage activity. The cleavage of antiQ by ABIQ was characterized using 5' rapid amplification of cDNA ends PCR and was located in an adenine-rich region of antiQ. We next generated a series of derivatives with point mutations within antiQ or with various numbers of antiQ repetitions. These modifications were analyzed for their effect on the antiphage activity (efficiency of plaquing) and on the endoribonuclease activity (Northern hybridization). We observed that increasing or reducing the number of antiQ repeats significantly decreased the antiphage activity of the system. Several point mutations had a similar effect on the antiphage activity and were associated with changes in the digestion profile of antiQ. Interestingly, a point mutation in the putative pseudoknot structure of antiQ mutants led to an increased AbiQ antiphage activity, thereby offering a novel way to increase the activity of an abortive infection mechanism.
authors.affiliation: Département de Biochimie, de Microbiologie et de Bio-informatique & PROTEO, Faculté des Sciences et Génie, GREB & Félix d'Hérelle Reference Center for Bacterial Viruses, Faculté de Médecine Dentaire, Université Laval, Québec City, Québec, Canada.
authors.forename: Maxime
authors.initials: M
authors.lastname: Bélanger
authors.affiliation: Département de Biochimie, de Microbiologie et de Bio-informatique & PROTEO, Faculté des Sciences et Génie, GREB & Félix d'Hérelle Reference Center for Bacterial Viruses, Faculté de Médecine Dentaire, Université Laval, Québec City, Québec, Canada Sylvain.Moineau@bcm.ulaval.ca.
authors.forename: Sylvain
authors.initials: S
authors.lastname: Moineau
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000235:genetics / Q000378:metabolism*; D001435:Bacteriophages / Q000254:growth & development; D015152:Blotting, Northern; D004252:DNA Mutational Analysis; D017045:Lactococcus / Q000235:genetics / Q000378:metabolism*; D050505:Mutant Proteins / Q000235:genetics / Q000378:metabolism; D022661:RNA, Untranslated / Q000235:genetics / Q000378:metabolism*; D010948:Viral Plaque Assay
chemical_list: C116791:AbiQ protein, Lactococcus lactis; D001426:Bacterial Proteins; D001427:Bacterial Toxins; D050505:Mutant Proteins; D022661:RNA, Untranslated
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