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Characterization of the Deep-Sea Streptomyces sp. SCSIO 02999 Derived VapC/VapB Toxin-Antitoxin System in Escherichia coli

1,*,†, 1,2,†, 1,2, 1,2 and 1,*
Key Laboratory of Tropical Marine Bio-resources and Ecology, Guangdong Key Laboratory of Marine Materia Medica, Research Network for Applied Microbiology (RNAM) Center for Marine Microbiology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou 510301, China
University of Chinese Academy of Sciences, Beijing 100049, China
Authors to whom correspondence should be addressed.
These authors contributed equally to this work.
Academic Editor: Anton Meinhart
Toxins 2016, 8(7), 195;
Received: 23 May 2016 / Revised: 13 June 2016 / Accepted: 20 June 2016 / Published: 1 July 2016
(This article belongs to the Special Issue Toxin-Antitoxin System in Bacteria)
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Toxin-antitoxin (TA) systems are small genetic elements that are ubiquitous in prokaryotes. Most studies on TA systems have focused on commensal and pathogenic bacteria; yet very few studies have focused on TAs in marine bacteria, especially those isolated from a deep sea environment. Here, we characterized a type II VapC/VapB TA system from the deep-sea derived Streptomyces sp. SCSIO 02999. The VapC (virulence-associated protein) protein belongs to the PIN (PilT N-terminal) superfamily. Overproduction of VapC strongly inhibited cell growth and resulted in a bleb-containing morphology in E. coli. The toxicity of VapC was neutralized through direct protein–protein interaction by a small protein antitoxin VapB encoded by a neighboring gene. Antitoxin VapB alone or the VapB/VapC complex negatively regulated the vapBC promoter activity. We further revealed that three conserved Asp residues in the PIN domain were essential for the toxic effect of VapC. Additionally, the VapC/VapB TA system stabilized plasmid in E. coli. Furthermore, VapC cross-activated transcription of several TA operons via a partially Lon-dependent mechanism in E. coli, and the activated toxins accumulated more preferentially than their antitoxin partners. Collectively, we identified and characterized a new deep sea TA system in the deep sea Streptomyces sp. and demonstrated that the VapC toxin in this system can cross-activate TA operons in E. coli. View Full-Text
Keywords: toxin-antitoxin; VapC/VapB; deep sea; Streptomyces toxin-antitoxin; VapC/VapB; deep sea; Streptomyces

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Guo, Y.; Yao, J.; Sun, C.; Wen, Z.; Wang, X. Characterization of the Deep-Sea Streptomyces sp. SCSIO 02999 Derived VapC/VapB Toxin-Antitoxin System in Escherichia coli. Toxins 2016, 8, 195.

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