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Cryo-EM structure of the Agrobacterium tumefaciens T4SS-associated T-pilus reveals stoichiometric protein-phospholipid assembly
Structure ( IF 5.7 ) Pub Date : 2023-03-03 , DOI: 10.1016/j.str.2023.02.005
Stefan Kreida 1 , Akihiro Narita 2 , Matthew D Johnson 3 , Elitza I Tocheva 4 , Anath Das 5 , Debnath Ghosal 6 , Grant J Jensen 7
Affiliation  

Agrobacterium tumefaciens causes crown gall disease in plants by the horizontal transfer of oncogenic DNA. The conjugation is mediated by the VirB/D4 type 4 secretion system (T4SS) that assembles an extracellular filament, the T-pilus, and is involved in mating pair formation between A. tumefaciens and the recipient plant cell. Here, we present a 3 Å cryoelectron microscopy (cryo-EM) structure of the T-pilus solved by helical reconstruction. Our structure reveals that the T-pilus is a stoichiometric assembly of the VirB2 major pilin and phosphatidylglycerol (PG) phospholipid with 5-start helical symmetry. We show that PG head groups and the positively charged Arg 91 residues of VirB2 protomers form extensive electrostatic interactions in the lumen of the T-pilus. Mutagenesis of Arg 91 abolished pilus formation. While our T-pilus structure is architecturally similar to previously published conjugative pili structures, the T-pilus lumen is narrower and positively charged, raising questions of whether the T-pilus is a conduit for ssDNA transfer.



中文翻译:

根癌农杆菌 T4SS 相关 T-菌毛的冷冻电镜结构揭示了化学计量的蛋白质-磷脂组装

根癌农杆菌通过致癌 DNA 的水平转移在植物中引起冠瘿病。这种结合是由 VirB/D4 4 型分泌系统 (T4SS) 介导的,该系统组装细胞外丝,即 T-菌毛,并参与根癌农杆菌之间的交配对形成和受体植物细胞。在这里,我们展示了通过螺旋重建解决的 T 菌毛的 3 Å 低温电子显微镜 (cryo-EM) 结构。我们的结构表明 T-菌毛是 VirB2 主要菌毛蛋白和磷脂酰甘油 (PG) 磷脂的化学计量组装体,具有 5-起始螺旋对称性。我们显示 PG 头部基团和带正电荷的 VirB2 原体的 Arg 91 残基在 T 菌毛的腔内形成广泛的静电相互作用。Arg 91 的诱变消除了菌毛的形成。虽然我们的 T 菌毛结构在结构上与先前发表的共轭菌毛结构相似,但 T 菌毛内腔更窄且带正电,这引发了人们对 T 菌毛是否是 ssDNA 转移的管道的疑问。

更新日期:2023-03-03
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