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Bacteria use conjugation systems, a subfamily of the type IV secretion systems, to transfer DNA to recipient cells. Despite 50 years of research, the architecture and mechanism of action of the channel mediating DNA transfer across the bacterial cell envelope remains obscure. By use of a sensitive, quantifiable assay termed transfer DNA immunoprecipitation(More)
Type IV secretion (T4S) systems are ancestrally related to bacterial conjugation machines. These systems assemble as a translocation channel, and often also as a surface filament or protein adhesin, at the envelopes of Gram-negative and Gram-positive bacteria. These organelles mediate the transfer of DNA and protein substrates to phylogenetically diverse(More)
Colicins are proteins produced by and toxic for some strains of Escherichia coli. They are produced by strains of E. coli carrying a colicinogenic plasmid that bears the genetic determinants for colicin synthesis, immunity, and release. Insights gained into each fundamental aspect of their biology are presented: their synthesis, which is under SOS(More)
The type VI secretion system (T6SS) is a complex and widespread gram-negative bacterial export pathway with the capacity to translocate protein effectors into a diversity of target cell types. Current structural models of the T6SS indicate that the apparatus is composed of at least two complexes, a dynamic bacteriophage-like structure and a(More)
The Tol-Pal system of Escherichia coli is required for the maintenance of outer membrane stability. Recently, proton motive force (pmf) has been found to be necessary for the co-precipitation of the outer membrane lipoprotein Pal with the inner membrane TolA protein, indicating that the Tol-Pal system forms a transmembrane link in which TolA is energized.(More)
Bacteria use type IV secretion systems (T4SS) to translocate DNA (T-DNA) and protein substrates across the cell envelope. By transfer DNA immunoprecipitation (TrIP), we recently showed that T-DNA translocates through the Agrobacterium tumefaciens VirB/D4 T4SS by forming close contacts sequentially with the VirD4 receptor, VirB11 ATPase, the inner membrane(More)
Bacteria use type IV secretion systems (T4SS) to translocate DNA and protein substrates to target cells of phylogenetically diverse taxa. Recently, by use of an assay termed transfer DNA immunoprecipitation (TrIP), we described the translocation route for a DNA substrate [T-DNA, portion of the Ti (tumor-inducing) plasmid that is transferred to plant cells](More)
The type IV secretion systems (T4SS) are widely distributed among the gram-negative and -positive bacteria. These systems mediate the transfer of DNA and protein substrates across the cell envelope to bacterial or eukaryotic cells generally through a process requiring direct cell-to-cell contact. Bacteria have evolved T4SS for survival during establishment(More)
Bacterial secretion systems are macromolecular complexes that release virulence factors into the medium or translocate them into the target host cell. These systems are widespread in bacteria allowing them to infect eukaryotic cells and survive or replicate within them. A new secretion system, the type VI secretion system (T6SS), was recently described and(More)
The outer membrane of gram-negative bacteria acts as a barrier against harmful lipophilic compounds and larger molecules unable to diffuse freely through the porins. However, outer membrane proteins together with the Tol-Pal and TonB systems have been exploited for the entry of macromolecules such as bacteriocins and phage DNA through the Escherichia coli(More)