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Biochem Biophys Res Commun. 2016 Sep 30;478(4):1521-7. doi: 10.1016/j.bbrc.2016.08.131. Epub 2016 Sep 4.

Structural insight into the E. coli HigBA complex.

Author information

1
School of Life Sciences, University of Dalian Science and Technology, Dalian, Liaolin Province, 230027, People's Republic of China.
2
Multi-disciplinary Research Center, Institute of High Energy Physics in Chinese Academy of Sciences, Beijing, 100049, People's Republic of China.
3
Multi-disciplinary Research Center, Institute of High Energy Physics in Chinese Academy of Sciences, Beijing, 100049, People's Republic of China. Electronic address: liuqsh@ihep.ac.cn.

Abstract

The toxin-antitoxin system is ubiquitously existed in bacteria and archaea, performing a wide variety of functions modulating cell fitness in response to environmental cues. In this report, we solved the crystal structure of the toxin-antitoxin HigBA complex from E. coli K-12 to 2.7 Å resolution. The crystal structure of the HigBA complex displays a hetero-tetramer (HigBA)2 form comprised by two HigB and two HigA subunits. Each toxin HigB resumes a microbial RNase T1 fold, characteristic of a three antiparallel β-sheet core shielded by a few α-helices at either side. Each antitoxin HigA composed of all α-helices resembles a "C"-shaped clamp nicely encompassing a HigB in the (HigBA)2 complex. Two HigA monomers dimerize at their N-terminal domain. We showed that HigA helix α1 was essential for HigA dimerization and the hetero-tetramer (HigBA)2 formation, but not for a hetero-dimeric HigBA formation. HigA dimerization mediated by helix α1 was dispensable for DNA-binding, as a heterodimeric HigBA complex still bound to the higBA operator in vitro. The HigA C-terminal domain with a helix-turn-helix fold was essential for DNA binding. We also defined two palindromes in higBA operator specifically recognized by HigA and HigBA in vitro.

KEYWORDS:

HigBA; Toxin-antitoxin

PMID:
27601326
DOI:
10.1016/j.bbrc.2016.08.131
[Indexed for MEDLINE]

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