scholarly journals In Situ Visualization of the pKM101-Encoded Type IV Secretion System Reveals a Highly Symmetric ATPase Energy Center

mBio ◽  
2021 ◽  
Author(s):  
Pratick Khara ◽  
Liqiang Song ◽  
Peter J. Christie ◽  
Bo Hu
Keyword(s):  
Electron Tomography ◽  
Cell Envelope ◽  
Type Iv Secretion ◽  
Secretion Systems ◽  
Type Iv ◽  
Cryo Electron Tomography ◽  
Plasmid Pkm101 ◽  
Energy Center ◽  
Bacterial Type

Bacterial type IV secretion systems (T4SSs) play central roles in antibiotic resistance spread and virulence. By cryo-electron tomography (CryoET), we solved the structure of the plasmid pKM101-encoded T4SS in the native context of the bacterial cell envelope.

scholarly journals Two type IV secretion systems with different functions in Burkholderia cenocepacia K56-2

Microbiology ◽  
2009 ◽  
Vol 155 (12) ◽  
pp. 4005-4013 ◽  
Author(s):  
Ruifu Zhang ◽  
John J. LiPuma ◽  
Carlos F. Gonzalez
Keyword(s):  
Type Iv Secretion ◽  
Burkholderia Cenocepacia ◽  
Target Cells ◽  
Secretion Systems ◽  
Type Iv ◽  
Plasmid Mobilization ◽  
Type Iv Secretion Systems ◽  
Derivative Plasmid ◽  
Chromosome Ii ◽  
Bacterial Type

Bacterial type IV secretion systems (T4SS) perform two fundamental functions related to pathogenesis: the delivery of effector molecules to eukaryotic target cells, and genetic exchange. Two T4SSs have been identified in Burkholderia cenocepacia K56-2, a representative of the ET12 lineage of the B. cepacia complex (Bcc). The plant tissue watersoaking (Ptw) T4SS encoded on a resident 92 kb plasmid is a chimera composed of VirB/D4 and F-specific subunits, and is responsible for the translocation of effector(s) that have been linked to the Ptw phenotype. The bc-VirB/D4 system located on chromosome II displays homology to the VirB/D4 T4SS of Agrobacterium tumefaciens. In contrast to the Ptw T4SS, the bc-VirB/D4 T4SS was found to be dispensable for Ptw effector(s) secretion, but was found to be involved in plasmid mobilization. The fertility inhibitor Osa did not affect the secretion of Ptw effector(s) via the Ptw system, but did disrupt the mobilization of a RSF1010 derivative plasmid.

scholarly journals Structural bases for F plasmid conjugation and F pilus biogenesis inEscherichia coli

2019 ◽  
Vol 116 (28) ◽  
pp. 14222-14227 ◽  
Author(s):  
Bo Hu ◽  
Pratick Khara ◽  
Peter J. Christie
Keyword(s):  
Cell Envelope ◽  
Type Iv Secretion ◽  
Bacterial Conjugation ◽  
Transfer System ◽  
F Plasmid ◽  
Physical Relationship ◽  
Type Iv ◽  
Pilus Biogenesis ◽  
Transfer Channel

Bacterial conjugation systems are members of the large type IV secretion system (T4SS) superfamily. Conjugative transfer of F plasmids residing in theEnterobacteriaceaewas first reported in the 1940s, yet the architecture of F plasmid-encoded transfer channel and its physical relationship with the F pilus remain unknown. We visualized F-encoded structures in the native bacterial cell envelope by in situ cryoelectron tomography (CryoET). Remarkably, F plasmids encode four distinct structures, not just the translocation channel or channel-pilus complex predicted by prevailing models. The F1 structure is composed of distinct outer and inner membrane complexes and a connecting cylinder that together house the envelope-spanning translocation channel. The F2 structure is essentially the F1 complex with the F pilus attached at the outer membrane (OM). Remarkably, the F3 structure consists of the F pilus attached to a thin, cell envelope-spanning stalk, whereas the F4 structure consists of the pilus docked to the OM without an associated periplasmic density. The traffic ATPase TraC is configured as a hexamer of dimers at the cytoplasmic faces of the F1 and F2 structures, where it respectively regulates substrate transfer and F pilus biogenesis. Together, our findings present architectural renderings of the DNA conjugation or “mating” channel, the channel–pilus connection, and unprecedented pilus basal structures. These structural snapshots support a model for biogenesis of the F transfer system and allow for detailed comparisons with other structurally characterized T4SSs.

scholarly journals Bacterial Type IV secretion systems: versatile virulence machines

2012 ◽  
Vol 7 (2) ◽  
pp. 241-257 ◽  
Author(s):  
Daniel E Voth ◽  
Laura J Broederdorf ◽  
Joseph G Graham
Keyword(s):  
Type Iv Secretion ◽  
Secretion Systems ◽  
Type Iv ◽  
Type Iv Secretion Systems ◽  
Bacterial Type

scholarly journals In Situ Visualization of the pKM101-Encoded Type IV Secretion System Reveals a Highly Symmetric ATPase Energy Center at the Channel Entrance

2021 ◽  
Author(s):  
Pratick Khara ◽  
Peter J. Christie ◽  
Bo Hu
Keyword(s):  
Cell Envelope ◽  
Secretion System ◽  
Type Iv Secretion ◽  
Type Iv Secretion System ◽  
Membrane Complex ◽  
Type Iv ◽  
Inner Membrane Complex ◽  
Cytoplasmic Complex

Bacterial conjugation systems are members of the type IV secretion system (T4SS) superfamily. T4SSs can be classified as ‘minimized’ or ‘expanded’ based on whether assembly requires only a core set of signature subunits or additional system-specific components. The prototypical ‘minimized’ systems mediating Agrobacterium tumefaciens T-DNA transfer and conjugative transfer of plasmids pKM101 and R388 are built from 12 subunits generically named VirB1-VirB11 and VirD4. In this study, we visualized the pKM101-encoded T4SS in the native context of the bacterial cell envelope by in situ cryoelectron tomography (CryoET). The T4SSpKM101 is composed of an outer membrane core complex (OMCC) connected by a thin stalk to an inner membrane complex (IMC). The OMCCexhibits 14-fold symmetry and resembles that of the T4SSR388, a large substructure of which was previously purified and analyzed by negative-stain electron microscopy (nsEM). The IMC of the in situ T4SSpKM101 machine is highly symmetrical and exhibits 6-fold symmetry, dominated by a hexameric collar in the periplasm and a cytoplasmic complex composed of a hexamer of dimers of the VirB4-like TraB ATPase. The IMCclosely resembles equivalent regions of three ‘expanded’ T4SSs previously visualized by in situ CryoET, but strikingly differs from the IMC of the purified T4SSR388 whose cytoplasmic complex instead presents as two side-by-side VirB4 hexamers.  Together, our findings support a unified architectural model for all T4SSs assembled in vivo regardless of their classification as ‘minimized’ or ‘expanded’: the signature VirB4-like ATPases invariably are arranged as central hexamers of dimers at the entrances to the T4SS channels.

scholarly journals The versatile bacterial type IV secretion systems

2003 ◽  
Vol 1 (2) ◽  
pp. 137-149 ◽  
Author(s):  
Eric Cascales ◽  
Peter J. Christie
Keyword(s):  
Type Iv Secretion ◽  
Secretion Systems ◽  
Type Iv ◽  
Type Iv Secretion Systems ◽  
Bacterial Type

VirB2 and VirB5 proteins: specialized adhesins in bacterial type-IV secretion systems?

2008 ◽  
Vol 16 (9) ◽  
pp. 409-413 ◽  
Author(s):  
Steffen Backert ◽  
Remi Fronzes ◽  
Gabriel Waksman
Keyword(s):  
Type Iv Secretion ◽  
Secretion Systems ◽  
Type Iv ◽  
Type Iv Secretion Systems ◽  
Bacterial Type

scholarly journals In situ ultrastructures of two evolutionarily distant apicomplexan rhoptry secretion systems

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shrawan Kumar Mageswaran ◽  
Amandine Guérin ◽  
Liam M. Theveny ◽  
William David Chen ◽  
Matthew Martinez ◽  
...  
Keyword(s):  
Cryptosporidium Parvum ◽  
Electron Tomography ◽  
Secretion System ◽  
Host Cells ◽  
Apical Region ◽  
Secretion Systems ◽  
Cryo Electron Tomography ◽  
Subtomogram Averaging ◽  
Secretory Apparatus

AbstractParasites of the phylum Apicomplexa cause important diseases including malaria, cryptosporidiosis and toxoplasmosis. These intracellular pathogens inject the contents of an essential organelle, the rhoptry, into host cells to facilitate invasion and infection. However, the structure and mechanism of this eukaryotic secretion system remain elusive. Here, using cryo-electron tomography and subtomogram averaging, we report the conserved architecture of the rhoptry secretion system in the invasive stages of two evolutionarily distant apicomplexans, Cryptosporidium parvum and Toxoplasma gondii. In both species, we identify helical filaments, which appear to shape and compartmentalize the rhoptries, and an apical vesicle (AV), which facilitates docking of the rhoptry tip at the parasite’s apical region with the help of an elaborate ultrastructure named the rhoptry secretory apparatus (RSA); the RSA anchors the AV at the parasite plasma membrane. Depletion of T. gondii Nd9, a protein required for rhoptry secretion, disrupts the RSA ultrastructure and AV-anchoring. Moreover, T. gondii contains a line of AV-like vesicles, which interact with a pair of microtubules and accumulate towards the AV, leading to a working model for AV-reloading and discharging of multiple rhoptries. Together, our analyses provide an ultrastructural framework to understand how these important parasites deliver effectors into host cells.

Bacterial type IV secretion systems: a tool for DNA transfer into mammalian cells

2009 ◽  
Vol 25 ◽  
pp. S35
Author(s):  
E. Fernández-González ◽  
H.D. de Paz ◽  
C. Dehio ◽  
F.J. Sangari ◽  
M. Llosa
Keyword(s):  
Mammalian Cells ◽  
Type Iv Secretion ◽  
Dna Transfer ◽  
Secretion Systems ◽  
Type Iv ◽  
Type Iv Secretion Systems ◽  
Bacterial Type
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