1. Structural insights into the T6 SS effector protein Tse3 and the Tse3- Tsi3 complex from P seudomonas aeruginosa reveal a calcium-dependent membrane-binding mechanism.
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Lu, Defen, Shang, Guijun, Zhang, Heqiao, Yu, Qian, Cong, Xiaoyan, Yuan, Jupeng, He, Fengjuan, Zhu, Chunyuan, Zhao, Yanyu, Yin, Kun, Chen, Yuanyuan, Hu, Junqiang, Zhang, Xiaodan, Yuan, Zenglin, Xu, Sujuan, Hu, Wei, Cang, Huaixing, and Gu, Lichuan
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BACTERIAL secretions ,PSEUDOMONAS aeruginosa ,BACTERIAL proteins ,PEPTIDOGLYCANS ,LYSOZYMES ,ANNEXINS - Abstract
The opportunistic pathogen P seudomonas aeruginosa uses the type VI secretion system ( T6 SS) to deliver the muramidase Tse3 into the periplasm of rival bacteria to degrade their peptidoglycan ( PG). Concomitantly, P . aeruginosa uses the periplasm-localized immunity protein Tsi3 to prevent potential self-intoxication caused by Tse3, and thus gains an edge over rival bacteria in fierce niche competition. Here, we report the crystal structures of Tse3 and the Tse3- Tsi3 complex. Tse3 contains an annexin repeat-like fold at the N-terminus and a G-type lysozyme fold at the C-terminus. One loop in the N-terminal domain ( Loop 12) and one helix (α9) from the C-terminal domain together anchor Tse3 and the Tse3- Tsi3 complex to membrane in a calcium-dependent manner in vitro, and this membrane-binding ability is essential for Tse3's activity. In the C-terminal domain, a Y-shaped groove present on the surface likely serves as the PG binding site. Two calcium-binding motifs are also observed in the groove and these are necessary for Tse3 activity. In the Tse3- Tsi3 structure, three loops of Tsi3 insert into the substrate-binding groove of Tse3, and three calcium ions present at the interface of the complex are indispensable for the formation of the Tse3- Tsi3 complex. [ABSTRACT FROM AUTHOR]
- Published
- 2014
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