F factor conjugation is a true type IV secretion system

Abstract

The F sex factor of Escherichia coli is a paradigm for bacterial conjugation and its transfer (tra) region represents a subset of the type IV secretion system (T4SS) family. The F tra region encodes eight of the 10 highly conserved (core) gene products of T4SS including TraAF (pilin), the TraBF, ‐KF (secretin‐like), ‐VF (lipoprotein) and TraCF (NTPase), ‐EF, ‐LF and TraGF (N‐terminal region) which correspond to TrbCP, ‐IP, ‐GP, ‐HP, ‐EP, ‐JP, DP and TrbLP, respectively, of the P‐type T4SS exemplified by the IncP plasmid RP4. F lacks homologs of TrbBP (NTPase) and TrbFP but contains a cluster of genes encoding proteins essential for F conjugation (TraFF, ‐HF, ‐UF, ‐WF, the C‐terminal region of TraGF, and TrbCF) that are hallmarks of F‐like T4SS. These extra genes have been implicated in phenotypes that are characteristic of F‐like systems including pilus retraction and mating pair stabilization. F‐like T4SS systems have been found on many conjugative plasmids and in genetic islands on bacterial chromosomes. Although few systems have been studied in detail, F‐like T4SS appear to be involved in the transfer of DNA only whereas P‐ and I‐type systems appear to transport protein or nucleoprotein complexes. This review examines the similarities and differences among the T4SS, especially F‐ and P‐like systems, and summarizes the properties of the F transfer region gene products.

Agrobacterium tumefaciens VirB6 Domains Direct the Ordered Export of a DNA Substrate Through a Type IV Secretion System

“…1 Over 75 VirB6-like proteins have been identified, all of which are known or postulated components of T4SS. 2,34 Despite overall low sequence similarities, VirB6-like proteins are highly hydrophobic with multiple predicted membrane-spanning segments. 2,34 Previous studies showed that several VirB proteins are rapidly degraded in virB6 null mutants, implicating VirB6 as important for assembly of a stable secretory apparatus.…”

“…2,34 Despite overall low sequence similarities, VirB6-like proteins are highly hydrophobic with multiple predicted membrane-spanning segments. 2,34 Previous studies showed that several VirB proteins are rapidly degraded in virB6 null mutants, implicating VirB6 as important for assembly of a stable secretory apparatus. 33,35,36 With the TrIP assay (this work), 16 we now have shown unequivocally that VirB6 participates directly in substrate trafficking.…”

“…1 One large T4SS subfamily, the conjugation systems, deliver DNA substrates to target cells by a mechanism dependent on formation of a mating junction between donor and recipient cells. 2 Conjugal DNA transfer is achieved through the coordinated actions of three distinct protein subcomplexes. 3 First, the DNA transfer and replication (Dtr) proteins initiate transfer by binding at the origin-of-transfer (oriT) sequence of a mobile DNA element, forming the relaxosome.…”

The versatile bacterial type IV secretion systems

“…The largest subfamily, the conjugation systems, are found in most species of Gram-negative and Grampositive bacteria. These systems mediate DNA transfer both within and between phylogenetically diverse species, and some systems even deliver DNA to fungi, plants and human cells 2,[9][10][11][12][13] . Conjugation is an important contributor to genome plasticity, and therefore bacterial fitness under changing environmental conditions, as encountered during infection of the human host.…”

Sensitivity analysis of Repast computational ecology models with R/Repast

“…The conjugative proficiency requires the expression of set of transmembrane proteins which are known collectively as type IV secretion systems (T4SS; Lawley, Klimke, Gubbins, & Frost, 2003). The presence of conjugative plasmids and the expression of conjugative machinery are detrimental for the host cell fitness (Rozkov et al., 2004), but there is no consensus on the valid ranges of metabolic costs imposed by the conjugative process.…”