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Identification and characterization of acetyltransferase‐type toxin‐antitoxin locus in Klebsiella pneumoniae
Author(s) -
Qian Hongliang,
Yao Qingqing,
Tai Cui,
Deng Zixin,
Gan Jianhua,
Ou HongYu
Publication year - 2018
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.13934
Subject(s) - biology , transcription (linguistics) , antitoxin , acetyltransferase , microbiology and biotechnology , klebsiella pneumoniae , toxin , genetics , gene , escherichia coli , acetylation , philosophy , linguistics
Summary A type II toxin‐antitoxin (TA) system, in which the toxin contains a Gcn5‐related N‐acetyltransferase (GNAT) domain, has been characterized recently. GNAT toxin acetylates aminoacyl‐tRNA and blocks protein translation. It is abolished by the cognate antitoxin that contains the ribbon‐helix‐helix (RHH) domain. Here, we present an experimental demonstration of the interaction of the GNAT‐RHH complex with TA promoter DNA. First, the GNAT‐RHH TA locus kacAT was found in Klebsiella pneumoniae HS11286, a strain resistant to multiple antibiotics. Overexpression of KacT halted cell growth and resulted in persister cell formation. The crystal structure also indicated that KacT is a typical acetyltransferase toxin. Co‐expression of KacA neutralized KacT toxicity. Expression of the bicistronic kacAT locus was up‐regulated during antibiotic stress. Finally, KacT and KacA formed a heterohexamer that interacted with promoter DNA, resulting in negative autoregulation of kacAT transcription. The N‐terminus region of KacA accounted for specific binding to the palindromic sequence on the operator DNA, whereas its C‐terminus region was essential for the inactivation of the GNAT toxin. These results provide an important insight into the regulation of the GNAT‐RHH family TA system.