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  • 1
    Online Resource
    Online Resource
    Berlin : Humboldt-Universität zu Berlin
    UID:
    edochu_18452_23074
    Format: 1 Online-Ressource (18 Seiten)
    Content: The bacterial flagellum and the related virulence-associated injectisome system of pathogenic bacteria utilize a type III secretion system (T3SS) to export substrate proteins across the inner membrane in a proton motive force-dependent manner. The T3SS is composed of an export gate (FliPQR/FlhA/FlhB) located in the flagellar basal body and an associated soluble ATPase complex in the cytoplasm (FliHIJ). Here, we summarise recent insights into the structure, assembly and protein secretion mechanisms of the T3SS with a focus on energy transduction and protein transport across the cytoplasmic membrane.
    Content: Peer Reviewed
    In: Basel : MDPI, 11,2
    Language: English
    URL: Volltext  (kostenfrei)
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  • 2
    UID:
    edochu_18452_25302
    Format: 1 Online-Ressource (12 Seiten)
    ISSN: 0950-382X , 0950-382X
    Content: 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.
    Content: Peer Reviewed
    In: Oxford [u.a.] : Wiley-Blackwell, 116,4, Seiten 1189-1200, 0950-382X
    Language: English
    URL: Volltext  (kostenfrei)
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  • 3
    UID:
    edochu_18452_26806
    Format: 1 Online-Ressource (9 Seiten)
    Content: The widespread bacterial second messenger bis-(3′-5′)-cyclic diguanosine monophosphate (c-di-GMP) is an important regulator of biofilm formation, virulence and cell differentiation. C-di-GMP-specific biosensors that allow detection and visualization of c-di-GMP levels in living cells are key to our understanding of how c-di-GMP fluctuations drive cellular responses. Here, we describe a novel c-di-GMP biosensor, CensYBL, that is based on c-di-GMP-induced dimerization of the effector protein BldD from Streptomyces resulting in bimolecular fluorescence complementation of split-YPet fusion proteins. As a proof-of-principle, we demonstrate that CensYBL is functional in detecting fluctuations in intracellular c-di-GMP levels in the Gram-negative model bacteria Escherichia coli and Salmonella enterica serovar Typhimurium. Using deletion mutants of c-di-GMP diguanylate cyclases and phosphodiesterases, we show that c-di-GMP dependent dimerization of CBldD-YPet results in fluorescence complementation reflecting intracellular c-di-GMP levels. Overall, we demonstrate that the CensYBL biosensor is a user-friendly and versatile tool that allows to investigate c-di-GMP variations using single-cell and population-wide experimental set-ups.
    Content: Peer Reviewed
    In: Oxford [u.a.] : Wiley-Blackwell, 117,3, Seiten 705-713
    Language: English
    URL: Volltext  (kostenfrei)
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  • 4
    UID:
    edochu_18452_25228
    Format: 1 Online-Ressource (12 Seiten)
    Content: Type-III secretion systems (T3SSs) of the bacterial flagellum and the evolutionarily related injectisome are capable of translocating proteins with a remarkable speed of several thousand amino acids per second. Here, we investigate how T3SSs are able to transport proteins at such a high rate while preventing the leakage of small molecules. Our mutational and evolutionary analyses demonstrate that an ensemble of conserved methionine residues at the cytoplasmic side of the T3SS channel create a deformable gasket (M-gasket) around fast-moving substrates undergoing export. The unique physicochemical features of the M-gasket are crucial to preserve the membrane barrier, to accommodate local conformational changes during active secretion, and to maintain stability of the secretion pore in cooperation with a plug domain (R-plug) and a network of salt-bridges. The conservation of the M-gasket, R-plug, and salt-bridge network suggests a universal mechanism by which the membrane integrity is maintained during high-speed protein translocation in all T3SSs.
    Content: Peer Reviewed
    Note: This article was supported by the German Research Foundation (DFG) and the Open Access Publication Fund of Humboldt-Universität zu Berlin.
    In: London : Nature Publishing Group UK, 12
    Language: English
    URL: Volltext  (kostenfrei)
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