An in vivo high-throughput screening approach targeting the type IV secretion system component VirB8 identified inhibitors of Brucella abortus 2308 proliferation.
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Anchoring the type VI secretion system to the peptidoglycan: TssL, TagL, TagP... what else?
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The recently identified bacterial type VI secretion system (T6SS) has rapidly become one of the most interesting areas of research in microbiology. In a relatively short period of time the relationship between the T6SS and the bacteriophage T4 tail and baseplate has been established. However, a number of questions concerning the T6SS remain the focus of a large number of researchers worldwide. Key questions that need to be addressed include how this system assembles in the cell envelope and the mechanism by which it translocates effector proteins across two membranes, the identification of such effectors and their function, how this secretion system contributes to virulence, interbacterial interactions and/or adaptation to the environment, and the evolutionary relationship between T6SS machine and bacteriophage T4. Focused on how the proteins constituting the secretion system interact, we recently identified a sub-complex of the T6SS comprised of four cell envelope proteins: the inner membrane-anchored TssL, TssM and TagL proteins and the outer membrane-associated TssJ lipoprotein. We further demonstrated that the TagL subunit carries a specific domain allowing anchorage of the secretion system to the peptidoglycan (PG) layer. Herein, we discuss these results, examine whether PG-binding motifs are found within other T6SS subunits and express hypotheses regarding the role of PG-binding motifs in type VI secretion. (+info)
The genome of the amoeba symbiont "Candidatus Amoebophilus asiaticus" encodes an afp-like prophage possibly used for protein secretion.
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The recently sequenced genome of the obligate intracellular amoeba symbiont 'Candidatus Amoebophilus asiaticus' is unique among prokaryotic genomes due to its extremely large fraction of genes encoding proteins harboring eukaryotic domains such as ankyrin-repeats, TPR/SEL1 repeats, leucine-rich repeats, as well as F- and U-box domains, most of which likely serve in the interaction with the amoeba host. Here we provide evidence for the presence of additional proteins which are presumably presented extracellularly and should thus also be important for host cell interaction. Surprisingly, we did not find homologues of any of the well-known protein secretion systems required to translocate effector proteins into the host cell in the A. asiaticus genome, and the type six secretion systems seems to be incomplete. Here we describe the presence of a putative prophage in the A. asiaticus genome, which shows similarity to the antifeeding prophage from the insect pathogen Serratia entomophila. In S. entomophila this system is used to deliver toxins into insect hosts. This putative antifeeding-like prophage might thus represent the missing protein secretion apparatus in A. asiaticus. (+info)
Enteropathogenic and enterohemorrhagic Escherichia coli type III secretion effector EspV induces radical morphological changes in eukaryotic cells.
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