Crystal Structure of Pseudomonas aeruginosa Tsi2 Reveals a Stably Folded Superhelical Antitoxin

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• 作者：Tingting Zou¹ ; ^&dagger ; ; Xue Yao¹ ; ^&dagger ; ; Bo Qin¹ ; Meng Zhang¹ ; Lifeng Cai² ; Weifeng Shang³ ; ¹ ; Dmitri I. Svergun³ ; Meitian Wang⁴ ; ^&Dagger ; ; ^{meitian.wang@psi.ch} ; Sheng Cui¹ ; ^&Dagger ; ; ^{cuisheng2007@yahoo.com.cn} ; Qi Jin¹ ; ^&Dagger ; ; ^{jinqi@ipbcams.ac.cn}
• 关键词：T6SS ; type VI secretion system ; TA ; toxin&ndash ; antitoxin ; ASU ; asymmetric unit ; SAXS ; small-angle X-ray scattering
• 刊名：Journal of Molecular Biology
• 出版年：2012
• 期刊代码：102_00222836
• 类别：imm
• 出版时间：6 April, 2012
• 卷：417
• 期：4
• 页码：351-361
• 文件大小：991 K

摘要

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聽脜 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.