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J Mol Biol. 2012 Apr 6;417(4):351-61. doi: 10.1016/j.jmb.2012.01.040. Epub 2012 Jan 30.

Crystal structure of Pseudomonas aeruginosa Tsi2 reveals a stably folded superhelical antitoxin.

Author information

1
Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 9 Dong Dan San Tiao, Beijing 100730, PR China.

Abstract

In the competition for niches in natural resources, Pseudomonas aeruginosa utilizes the type VI secretion system to inject the toxic protein effector Tse2 into bacteria on cell-cell contact. The cytoplasm toxin immunity protein Tsi2 can neutralize Tse2 by physical interaction with the toxin, providing essential protection from toxin activity. Except for orthologues in P. aeruginosa, Tsi2 antitoxin does not share detectable sequence homology with known proteins in public databases. The mechanism underlying toxin neutralization by Tsi2 remains unknown. We report here the crystal structure of Tsi2 at 2.28 Å resolution. Our structural and biophysical analyses demonstrate that the antitoxin adopts a previously unobserved superhelical conformation. Tsi2 is highly thermostable in the absence of the toxin in solution. Tsi2 assembles a dimer with 2-fold rotational symmetry, similar to that observed in other toxin-antitoxin systems. Dimerization is essential for the stable folding of Tsi2.

PMID:
22310046
DOI:
10.1016/j.jmb.2012.01.040
[Indexed for MEDLINE]

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