Crystal structure of the soluble domain of TrwG Type IV secretion machinery from Bartonella grahamii

Experimental Data Snapshot

  • Resolution: 2.00 Å
  • R-Value Free: 0.240 
  • R-Value Work: 0.195 
  • R-Value Observed: 0.198 

Starting Model: experimental
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wwPDB Validation   3D Report Full Report

This is version 1.3 of the entry. See complete history


Structural Insight into How Bacteria Prevent Interference between Multiple Divergent Type IV Secretion Systems.

Gillespie, J.J.Phan, I.Q.Scheib, H.Subramanian, S.Edwards, T.E.Lehman, S.S.Piitulainen, H.Rahman, M.S.Rennoll-Bankert, K.E.Staker, B.L.Taira, S.Stacy, R.Myler, P.J.Azad, A.F.Pulliainen, A.T.

(2015) mBio 6: e01867-e01815

  • DOI: https://doi.org/10.1128/mBio.01867-15
  • Primary Citation of Related Structures:  
    4JF8, 4KZ1, 4LSO, 4MEI, 4NHF, 4O3V

  • PubMed Abstract: 

    Prokaryotes use type IV secretion systems (T4SSs) to translocate substrates (e.g., nucleoprotein, DNA, and protein) and/or elaborate surface structures (i.e., pili or adhesins). Bacterial genomes may encode multiple T4SSs, e.g., there are three functionally divergent T4SSs in some Bartonella species (vir, vbh, and trw). In a unique case, most rickettsial species encode a T4SS (rvh) enriched with gene duplication. Within single genomes, the evolutionary and functional implications of cross-system interchangeability of analogous T4SS protein components remains poorly understood. To lend insight into cross-system interchangeability, we analyzed the VirB8 family of T4SS channel proteins. Crystal structures of three VirB8 and two TrwG Bartonella proteins revealed highly conserved C-terminal periplasmic domain folds and dimerization interfaces, despite tremendous sequence divergence. This implies remarkable structural constraints for VirB8 components in the assembly of a functional T4SS. VirB8/TrwG heterodimers, determined via bacterial two-hybrid assays and molecular modeling, indicate that differential expression of trw and vir systems is the likely barrier to VirB8-TrwG interchangeability. We also determined the crystal structure of Rickettsia typhi RvhB8-II and modeled its coexpressed divergent paralog RvhB8-I. Remarkably, while RvhB8-I dimerizes and is structurally similar to other VirB8 proteins, the RvhB8-II dimer interface deviates substantially from other VirB8 structures, potentially preventing RvhB8-I/RvhB8-II heterodimerization. For the rvh T4SS, the evolution of divergent VirB8 paralogs implies a functional diversification that is unknown in other T4SSs. Collectively, our data identify two different constraints (spatiotemporal for Bartonella trw and vir T4SSs and structural for rvh T4SSs) that mediate the functionality of multiple divergent T4SSs within a single bacterium. Assembly of multiprotein complexes at the right time and at the right cellular location is a fundamentally important task for any organism. In this respect, bacteria that express multiple analogous type IV secretion systems (T4SSs), each composed of around 12 different components, face an overwhelming complexity. Our work here presents the first structural investigation on factors regulating the maintenance of multiple T4SSs within a single bacterium. The structural data imply that the T4SS-expressing bacteria rely on two strategies to prevent cross-system interchangeability: (i) tight temporal regulation of expression or (ii) rapid diversification of the T4SS components. T4SSs are ideal drug targets provided that no analogous counterparts are known from eukaryotes. Drugs targeting the barriers to cross-system interchangeability (i.e., regulators) could dysregulate the structural and functional independence of discrete systems, potentially creating interference that prevents their efficient coordination throughout bacterial infection.

  • Organizational Affiliation

    Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, USA JGillespie@som.umaryland.edu arto.pulliainen@utu.fi.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
TrwG protein
A, B, C, D, E
A, B, C, D, E, F
180Bartonella grahamii as4aupMutation(s): 0 
Gene Names: Bgr_19310trwG
Find proteins for C6AAT5 (Bartonella grahamii (strain as4aup))
Explore C6AAT5 
Go to UniProtKB:  C6AAT5
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupC6AAT5
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

Unit Cell:
Length ( Å )Angle ( ˚ )
a = 62.95α = 90
b = 87.65β = 90
c = 191.83γ = 90
Software Package:
Software NamePurpose
XSCALEdata scaling
PDB_EXTRACTdata extraction
XDSdata reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2014-03-05
    Type: Initial release
  • Version 1.1: 2015-12-16
    Changes: Database references
  • Version 1.2: 2016-03-23
    Changes: Database references
  • Version 1.3: 2023-09-20
    Changes: Data collection, Database references, Derived calculations, Refinement description