Interaction of <i>Bacteroides fragilis</i> pLV22a relaxase and transfer DNA with <i>Escherichia coli</i> RP4‐TraG coupling protein

Thomas, Johnson; Hecht, David W.

doi:10.1111/j.1365-2958.2007.05967.x

Cited by 12 publications

(9 citation statements)

References 54 publications

(121 reference statements)

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“…This interaction was detected in A. tumefaciens mutants lacking VirB channel components, confirming that the T4CP functions as a substrate receptor even independently of the channel components (49). Similar lines of investigation have now established that B. fragilis pLV22a (which can translocate through the plasmid RP4 T4SS) binds the TraG RP4 T4CP (262) and that the E. faecalis pCF10 transfer intermediate binds the PcfC pCF10 T4CP (59).…”

Section: Substrate Receptor Activitysupporting

confidence: 55%

Biological Diversity of Prokaryotic Type IV Secretion Systems

Martı́nez

Christie

2009

Microbiol Mol Biol Rev

622

780

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SUMMARY Type IV secretion systems (T4SS) translocate DNA and protein substrates across prokaryotic cell envelopes generally by a mechanism requiring direct contact with a target cell. Three types of T4SS have been described: (i) conjugation systems, operationally defined as machines that translocate DNA substrates intercellularly by a contact-dependent process; (ii) effector translocator systems, functioning to deliver proteins or other macromolecules to eukaryotic target cells; and (iii) DNA release/uptake systems, which translocate DNA to or from the extracellular milieu. Studies of a few paradigmatic systems, notably the conjugation systems of plasmids F, R388, RP4, and pKM101 and the Agrobacterium tumefaciens VirB/VirD4 system, have supplied important insights into the structure, function, and mechanism of action of type IV secretion machines. Information on these systems is updated, with emphasis on recent exciting structural advances. An underappreciated feature of T4SS, most notably of the conjugation subfamily, is that they are widely distributed among many species of gram-negative and -positive bacteria, wall-less bacteria, and the Archaea. Conjugation-mediated lateral gene transfer has shaped the genomes of most if not all prokaryotes over evolutionary time and also contributed in the short term to the dissemination of antibiotic resistance and other virulence traits among medically important pathogens. How have these machines adapted to function across envelopes of distantly related microorganisms? A survey of T4SS functioning in phylogenetically diverse species highlights the biological complexity of these translocation systems and identifies common mechanistic themes as well as novel adaptations for specialized purposes relating to the modulation of the donor-target cell interaction.

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Section: Substrate Receptor Activitysupporting

confidence: 55%

Biological Diversity of Prokaryotic Type IV Secretion Systems

Martı́nez

Christie

2009

Microbiol Mol Biol Rev

622

780

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“…This C-terminal region has been shown to mediate the delivery of a fused reporter protein to plant cells, confirming that it carries sufficient information for docking with and translocation through the VirB/VirD4 T4SS (45,46). Finally, studies of several conjugation systems have provided compelling evidence that relaxases interact directly with their cognate T4CPs (60)(61)(62). Taken together, therefore, our data strongly indicate that VirD2 mediates DNA substrate docking with VirD4 via its C terminus and that this interaction is essential for activation of VirB10.…”

Section: Discussionmentioning

confidence: 89%

DNA Substrate-Induced Activation of the Agrobacterium VirB/VirD4 Type IV Secretion System

et al. 2013

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The bitopic membrane protein VirB10 of the Agrobacterium VirB/VirD4 type IV secretion system (T4SS) undergoes a structural transition in response to sensing of ATP binding or hydrolysis by the channel ATPases VirD4 and VirB11. This transition, detectable as a change in protease susceptibility, is required for DNA substrate passage through the translocation channel. Here, we present evidence that DNA substrate engagement with VirD4 and VirB11 also is required for activation of VirB10. Several DNA substrates (oncogenic T-DNA and plasmids RSF1010 and pCloDF13) induced the VirB10 conformational change, each by mechanisms requiring relaxase processing at cognate oriT sequences. VirD2 relaxase deleted of its translocation signal or any of the characterized relaxases produced in the absence of cognate DNA substrates did not induce the structural transition. Translocated effector proteins, e.g., VirE2, VirE3, and VirF, also did not induce the transition. By mutational analyses, we supplied evidence that the N-terminal periplasmic loop of VirD4, in addition to its catalytic site, is essential for early-stage DNA substrate transfer and the VirB10 conformational change. Further studies of VirB11 mutants established that three T4SS-mediated processes, DNA transfer, protein transfer, and pilus production, can be uncoupled and that the latter two processes proceed independently of the VirB10 conformational change. Our findings support a general model whereby DNA ligand binding with VirD4 and VirB11 stimulates ATP binding/hydrolysis, which in turn activates VirB10 through a structural transition. This transition confers an open-channel configuration enabling passage of the DNA substrate to the cell surface.T he type IV secretion systems (T4SSs) mediate the transfer of DNA and protein substrates across the envelopes of many Gram-negative and -positive bacterial species (1). The conjugation systems comprise a large subfamily of the T4SSs. These medically important systems are responsible for widespread transmission of antibiotic resistance genes and virulence genes carried by conjugative plasmids and chromosomally integrated elements. Overall, conjugation can be depicted as three distinct biochemical reactions. The DNA transfer and replication (Dtr) proteins bind a cognate origin-of-transfer (oriT) sequence and initiate processing of the DNA substrate for transfer (2-4). Next, the Dtr-oriT complex, termed the relaxosome, engages with the type IV coupling protein (T4CP) (5). Finally, the T4CP delivers the DNA substrate to a transenvelope channel comprised of the mating pair formation (Mpf) proteins for translocation across the cell envelope (6, 7). Studies in recent years have begun to define mechanistic and structural details of conjugation systems. Additionally, an accumulating body of evidence suggests that a combination of intraand extracellular signals act to coordinate the conjugative DNA transfer reactions in space and time. The present investigations advance our understanding of a signaling mechanism required for DNA subs...

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“…In A. tumefaciens , the TrIP studies showed that the VirD4 T4CP binds the T-DNA substrate independently of the VirB subunits and also by a mechanism dependent on processing of the T-DNA by the VirD2 relaxase [38]. Bacillus fragilis plasmid pLV22a also was shown to form a formaldeyde-crosslinkable contact with the TraG RP4 T4CP [83], and Enterococcus faecalis pCF10 with the PcfC pCF10 T4CP [31]. Complementary in vitro studies have identified interactions between T4CPs and relaxosome components or protein substrates, and also demonstrated stimulatory effects of purified T4CPs on relaxase cleavage reactions [1, 23, 84].…”

Section: The T4cp Substrate Receptormentioning

confidence: 99%

Mechanism and structure of the bacterial type IV secretion systems

Christie¹,

Whitaker²,

González-Rivera³

2014

Biochimica et Biophysica Acta (BBA) - Molecular Cell Research

240

209

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The bacterial type IV secretion systems (T4SSs) translocate DNA and protein substrates to bacterial or eukaryotic target cells generally by a mechanism dependent on direct cell-to-cell contact. The T4SSs encompass two large subfamilies, the conjugation systems and the effector translocators. The conjugation systems mediate interbacterial DNA transfer and are responsible for the rapid dissemination of antibiotic resistance genes and virulence determinants in clinical settings. The effector translocators are used by many Gram-negative bacterial pathogens for delivery of potentially hundreds of virulence proteins to eukaryotic cells for modulation of different physiological processes during infection. Recently, there has been considerable progress in defining the structures of T4SS machine subunits and large machine subassemblies. Additionally, the nature of substrate translocation sequences and the contributions of accessory proteins to substrate docking with the translocation channel have been elucidated. A DNA translocation route through the Agrobacterium tumefaciens VirB/VirD4 system was defined, and both intracellular (DNA ligand, ATP energy) and extracellular (phage binding) signals were shown to activate type IV-dependent translocation. Finally, phylogenetic studies have shed light on the evolution and distribution of T4SSs, and complementary structure-function studies of diverse systems have identified adaptations tailored for novel functions in pathogenic settings. This review summarizes the recent progress in our understanding of the architecture and mechanism of action of these fascinating machines, with emphasis on the ‘archetypal’ A. tumefaciens VirB/VirD4 T4SS and related conjugation systems.

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Interaction of Bacteroides fragilis pLV22a relaxase and transfer DNA with Escherichia coli RP4‐TraG coupling protein

Cited by 12 publications

References 54 publications

Biological Diversity of Prokaryotic Type IV Secretion Systems

Biological Diversity of Prokaryotic Type IV Secretion Systems

DNA Substrate-Induced Activation of the Agrobacterium VirB/VirD4 Type IV Secretion System

Mechanism and structure of the bacterial type IV secretion systems

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