ジャーナル: Nat Microbiol / 年: 2018 タイトル: Mechanism of loading and translocation of type VI secretion system effector Tse6. 著者: Dennis Quentin / Shehryar Ahmad / Premy Shanthamoorthy / Joseph D Mougous / John C Whitney / Stefan Raunser / 要旨: The type VI secretion system (T6SS) primarily functions to mediate antagonistic interactions between contacting bacterial cells, but also mediates interactions with eukaryotic hosts. This molecular ...The type VI secretion system (T6SS) primarily functions to mediate antagonistic interactions between contacting bacterial cells, but also mediates interactions with eukaryotic hosts. This molecular machine secretes antibacterial effector proteins by undergoing cycles of extension and contraction; however, how effectors are loaded into the T6SS and subsequently delivered to target bacteria remains poorly understood. Here, using electron cryomicroscopy, we analysed the structures of the Pseudomonas aeruginosa effector Tse6 loaded onto the T6SS spike protein VgrG1 in solution and embedded in lipid nanodiscs. In the absence of membranes, Tse6 stability requires the chaperone EagT6, two dimers of which interact with the hydrophobic transmembrane domains of Tse6. EagT6 is not directly involved in Tse6 delivery but is crucial for its loading onto VgrG1. VgrG1-loaded Tse6 spontaneously enters membranes and its toxin domain translocates across a lipid bilayer, indicating that effector delivery by the T6SS does not require puncturing of the target cell inner membrane by VgrG1. Eag chaperone family members from diverse Proteobacteria are often encoded adjacent to putative toxins with predicted transmembrane domains and we therefore anticipate that our findings will be generalizable to numerous T6SS-exported membrane-associated effectors.
全体 : Type VI secretion "pre-firing" VgrG1-Tse6-EagT6-EF-Tu-Tsi6 complex
全体
名称: Type VI secretion "pre-firing" VgrG1-Tse6-EagT6-EF-Tu-Tsi6 complex
要素
複合体: Type VI secretion "pre-firing" VgrG1-Tse6-EagT6-EF-Tu-Tsi6 complex
複合体: Valine-glycine repeat protein 1
タンパク質・ペプチド: VgrG1
複合体: Type VI secretion exported 6
複合体: Type VI secretion immunity 6
複合体: Effector associated gene with tse6
複合体: Elongation factor Tu 1
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超分子 #1: Type VI secretion "pre-firing" VgrG1-Tse6-EagT6-EF-Tu-Tsi6 complex
超分子
名称: Type VI secretion "pre-firing" VgrG1-Tse6-EagT6-EF-Tu-Tsi6 complex タイプ: complex / ID: 1 / 親要素: 0 / 含まれる分子: all 詳細: The type VI "pre-firing" complex consists of a single copy of Tse6, EF-Tu, Tsi6 and trimeric VgrG1 as well as two copies of dimeric EagT6.
分子量
理論値: 43 KDa
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超分子 #2: Valine-glycine repeat protein 1
超分子
名称: Valine-glycine repeat protein 1 / タイプ: complex / ID: 2 / 親要素: 1 / 含まれる分子: all / 詳細: VgrG1 forms a trimer - UniProt Identifier: Q9I741
名称: Effector associated gene with tse6 / タイプ: complex / ID: 5 / 親要素: 1 詳細: EagT6 forms dimers - UniProt identifier: Q9I738. Two dimers are present in the EM map.