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Protein Secretion System (protein + secretion_system)
Selected AbstractsProtein secretion systems in MycobacteriaCELLULAR MICROBIOLOGY, Issue 6 2007Patricia A. DiGiuseppe Champion Summary Mycobacteria have a unique cell-envelope structure which protects the bacteria from the extracellular environment by limiting access to noxious molecules from the outside. This extremely hydrophobic and thick barrier also poses a unique problem for the export of bacterial products. Here we review the multiple protein secretion pathways in Mycobacteria, including the general secretion pathway and the Twin-Arginine Transporter, with an emphasis on the ESX-1 alternate secretion system. This newly identified protein secretion system is required for growth during infection and has provided insight into how M. tuberculosis manipulates the host immune response during infection. [source] Identification of novel hrp -regulated genes through functional genomic analysis of the Pseudomonas syringae pv. tomato DC3000 genomeMOLECULAR MICROBIOLOGY, Issue 5 2002Julie Zwiesler-Vollick Summary Pseudomonas syringae pv. tomato ( Pst ) strain DC3000 infects the model plants Arabidopsis thaliana and tomato, causing disease symptoms characterized by necrotic lesions surrounded by chlorosis. One mechanism used by Pst DC3000 to infect host plants is the type III protein secretion system, which is thought to deliver multiple effector proteins to the plant cell. The exact number of type III effectors in Pst DC3000 or any other plant pathogenic bacterium is not known. All known type III effector genes of P. syringae are regulated by HrpS, an NtrC family protein, and the HrpL alternative sigma factor, which presumably binds to a conserved cis element (called the ,hrp box') in the promoters of type III secretion-associated genes. In this study, we designed a search motif based on the promoter sequences conserved in 12 published hrp operons and putative effector genes in Pst DC3000. Seventy-three predicted genes were retrieved from the January 2001 release of the Pst DC3000 genome sequence, which had 95% genome coverage. The expression of the 73 genes was analysed by microarray and Northern blotting, revealing 24 genes/operons (including eight novel genes), the expression of which was consistently higher in hrp -inducing minimal medium than in nutrient-rich Luria,Bertani broth. Expression of all eight genes was dependent on the hrpS gene. Most were also dependent on the hrpL gene, but at least one was dependent on the hrpS gene, but not on the hrpL gene. An AvrRpt2-based type III translocation assay provides evidence that some of the hrpS -regulated novel genes encode putative effector proteins. [source] Erwinia amylovora modifies phenolic profiles of susceptible and resistant apple through its type III secretion systemPHYSIOLOGIA PLANTARUM, Issue 3 2008Isabelle Pontais Fire blight is a disease affecting Maloideae caused by the necrogenic bacterium Erwinia amylovora, which requires the type III protein secretion system (TTSS) for pathogenicity. Profiles of methanol-extractable leaf phenolics of two apple (Malus × domestica) genotypes with contrasting susceptibility to this disease were analyzed by HPLC after infection. Some qualitative differences were recorded between the constitutive compositions of the two genotypes but in both of them dihydrochalcones accounted for more than 90% of total phenolics. Principal component analysis separated leaves inoculated with a virulent wild-type strain from those inoculated with a non-pathogenic TTSS-defective mutant or with water. The changes in levels of the various groups of phenolics in response to the virulent bacterium were similar between the two genotypes, with a significant decrease of dihydrochalcones and a significant increase of hydroxycinnamate derivatives. Differences between genotypes were, however, recorded in amplitude and kinetic of variation in these groups. Occurrence of oxidation and polymerization reactions is proposed, based on the browning process of infected tissues, but whether some by-products act in defense as toxic compounds remain to be tested. Among direct antibacterial constitutive compounds present in apple leaves, the dihydrochalcone phloretin only was found at levels close to lethal concentrations in both genotypes. However, E. amylovora exhibited the ability to stabilize this compound at sublethal levels even in the resistant apple, rejecting the hypothesis of its involvement in the resistance of this genotype. [source] Protein secretion systems in MycobacteriaCELLULAR MICROBIOLOGY, Issue 6 2007Patricia A. DiGiuseppe Champion Summary Mycobacteria have a unique cell-envelope structure which protects the bacteria from the extracellular environment by limiting access to noxious molecules from the outside. This extremely hydrophobic and thick barrier also poses a unique problem for the export of bacterial products. Here we review the multiple protein secretion pathways in Mycobacteria, including the general secretion pathway and the Twin-Arginine Transporter, with an emphasis on the ESX-1 alternate secretion system. This newly identified protein secretion system is required for growth during infection and has provided insight into how M. tuberculosis manipulates the host immune response during infection. [source] Extracellular biology of Myxococcus xanthusFEMS MICROBIOLOGY REVIEWS, Issue 2 2010Anna Konovalova Abstract Myxococcus xanthus has a lifecycle characterized by several social interactions. In the presence of prey, M. xanthus is a predator forming cooperatively feeding colonies, and in the absence of nutrients, M. xanthus cells interact to form multicellular, spore-filled fruiting bodies. Formation of both cellular patterns depends on extracellular functions including the extracellular matrix and intercellular signals. Interestingly, the formation of these patterns also depends on several activities that involve direct cell,cell contacts between M. xanthus cells or direct contacts between M. xanthus cells and the substratum, suggesting that M. xanthus cells have a marked ability to distinguish self from nonself. Genome-wide analyses of the M. xanthus genome reveal a large potential for protein secretion. Myxococcus xanthus harbours all protein secretion systems required for translocation of unfolded and folded proteins across the cytoplasmic membrane and an intact type II secretion system. Moreover, M. xanthus contains 60 ATP-binding cassette transporters, two degenerate type III secretion systems, both of which lack the parts in the outer membrane and the needle structure, and an intact type VI secretion system for one-step translocation of proteins across the cell envelope. Also, analyses of the M. xanthus proteome reveal a large protein secretion potential including many proteins of unknown function. [source] Show me the substrates: modulation of host cell function by type IV secretion systemsCELLULAR MICROBIOLOGY, Issue 6 2003Hiroki Nagai Summary Evidence for the involvement of type IV protein secretion systems in bacterial virulence is accumulating. Many of the substrate proteins secreted by type IV systems either hijack or interfere with specific host cell pathways. These substrates can be injected directly into host cells via the type IV apparatus or are secreted by the type IV machinery in a state that allows them to gain access to cellular targets without the further assistance of the type IV system. Arguably, the protein substrates of most type IV secretion systems remain undiscovered. Here, we review the activities of known type IV substrates and discuss the putative roles of unidentified substrates. [source] | ||||||||||