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Structure and activity of AbiQ , a lactococcal endoribonuclease belonging to the type III toxin–antitoxin system
Author(s) -
Samson Julie E.,
Spinelli Silvia,
Cambillau Christian,
Moineau Sylvain
Publication year - 2013
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12129
Subject(s) - endoribonuclease , biology , antitoxin , plasmid , microbiology and biotechnology , rnase p , toxin , bacteriophage , nuclease , virulence , rna , gene , escherichia coli , genetics
Summary AbiQ is a phage resistance mechanism found on a native plasmid of L actococcus 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. N orthern and W estern 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.