Crystal structure of Pseudomonas aeruginosa Tsi2 reveals a stably folded superhelical antitoxin.
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.
Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, No. 9 Dong Dan San Tiao, Beijing 100730, PR China.
Tingting
T
Zou
Xue
X
Yao
Bo
B
Qin
Meng
M
Zhang
Lifeng
L
Cai
Weifeng
W
Shang
Dmitri I
DI
Svergun
Meitian
M
Wang
Sheng
S
Cui
Qi
Q
Jin
D000595:Amino Acid Sequence; D000992:Antitoxins / Q000737:chemistry*; D001426:Bacterial Proteins / Q000737:chemistry; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D017510:Protein Folding; D055503:Protein Multimerization; D055550:Protein Stability; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D014118:Toxins, Biological / Q000737:chemistry
D000992:Antitoxins; D001426:Bacterial Proteins; D014118:Toxins, Biological