Format

Send to

Choose Destination
Biochim Biophys Acta. 2014 Aug;1843(8):1578-91. doi: 10.1016/j.bbamcr.2013.12.019. Epub 2014 Jan 2.

Mechanism and structure of the bacterial type IV secretion systems.

Author information

1
Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA. Electronic address: Peter.J.Christie@uth.tmc.edu.
2
Department of Microbiology and Molecular Genetics, UT-Houston Medical School, 6431 Fannin, JFB1.765, Houston, TX 77030, USA.

Abstract

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. This article is part of a Special Issue entitled: Protein trafficking and secretion in bacteria. Guest Editors: Anastassios Economou and Ross Dalbey.

KEYWORDS:

Conjugation; DNA transfer; Pathogenesis; Pilus; Protein translocation; Traffic ATPase

PMID:
24389247
PMCID:
PMC4061277
DOI:
10.1016/j.bbamcr.2013.12.019
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center