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Hook-basal-body assembly state dictates substrate specificity of the flagellar type-III secretion system
Molecular Microbiology ( IF 3.6 ) Pub Date : 2021-08-31 , DOI: 10.1111/mmi.14805
Alina Guse 1, 2 , Manuel Halte 1 , Svenja Hüsing 1 , Marc Erhardt 1, 3
Affiliation  

The assembly of the bacterial flagellum is orchestrated by the secretion of distinct early and late secretion substrates via the flagellar-specific type-III secretion system (fT3SS). However, how the fT3SS is able to distinguish between the different (early and late) substrate classes during flagellar assembly remains poorly understood. In this study, we investigated the substrate selectivity and specificity of the fT3SS of Salmonella enterica at different assembly stages. For this, we developed an experimental setup that allowed us to synchronize hook-basal-body assembly and to monitor early and late substrate secretion of fT3SSs operating in either early or late secretion mode, respectively. Our results demonstrate that the fT3SS features a remarkable specificity for only the substrates required at the respective assembly stage. No crosstalk of substrates was observed for fT3SSs operating in the opposing secretion mode. We further found that a substantial fraction of fT3SS surprisingly remained in early secretion mode. Our results thus suggest that the secretion substrate specificity switch of the fT3SS is unidirectional and irreversible. The developed secretion substrate reporter system further provides a platform for future investigations of the underlying molecular mechanisms of the elusive substrate recognition of the T3SS.

中文翻译:

钩基体组装状态决定了鞭毛 III 型分泌系统的底物特异性

细菌鞭毛的组装是通过鞭毛特异性 III 型分泌系统 (fT3SS) 分泌不同的早期和晚期分泌底物来协调的。然而,在鞭毛组装过程中,fT3SS 如何区分不同(早期和晚期)底物类别仍然知之甚少。在这项研究中,我们研究了肠沙门氏菌fT3SS 的底物选择性和特异性。在不同的组装阶段。为此,我们开发了一个实验装置,使我们能够同步钩基体组装,并分别监测在早期或晚期分泌模式下运行的 fT3SS 的早期和晚期底物分泌。我们的结果表明,fT3SS 仅对相应组装阶段所需的基板具有显着的特异性。对于以相反分泌模式运行的 fT3SS,未观察到底物串扰。我们进一步发现,很大一部分 fT3SS 出人意料地保持在早期分泌模式。因此,我们的结果表明 fT3SS 的分泌底物特异性开关是单向且不可逆的。
更新日期:2021-10-25
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