Premium
The role of F plasmid TraF and TrbB in stabilizing the conjugative apparatus
Author(s) -
Frost Laura Susan,
Klinger Barbara,
Manchak Jan,
Elton Trevor Charles,
Audette Gerald
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a96-b
Subject(s) - pilus , bacterial conjugation , dsba , plasmid , scaffold protein , secretion , chemistry , escherichia coli , biology , microbiology and biotechnology , dna , biochemistry , signal transduction , gene , periplasmic space
The role of two proteins, TrbB and TraF, encoded by the F plasmid, were investigated for their ability to affect F transfer protein localization and stability using cell fractionation by sucrose gradient sedimentation and immunoblot analyses. Bacterial conjugation mediates the horizontal transfer of genetic material throughout the microbial world. The F plasmid contains a transfer region that encodes a type IV secretion system (T4SS) necessary for conjugative pilus assembly and DNA transfer. The F‐type T4SS are considerably more complex than the P‐type systems because of the properties of pilus retraction and stable mating pair formation. The proteins that are specific to F‐T4SS are TraF, ‐G (C‐terminal domain), TraH, ‐N, ‐U, ‐W, TrbB, ‐C and‐I. TraG, ‐N and ‐U are important for mating pair stabilization and the remaining proteins are required for pilus assembly and retraction. Several F‐T4SS proteins are remarkable for their high cysteine content (TraN, TraU and TraH have 22, 10 and 6 cysteines, respectively). TraF and TrbB, have thioredoxin‐folds with TrbB, but not TraF, having a characteristic CxxC motif. Previously, we have shown TrbB has DsbC‐like activity and acts as a disulfide bond isomerase since, like DsbC, it can partially complement a dsbA mutation. Whereas TrbB is not essential for conjugation, TraF is required for pilus assembly and transfer, suggesting that it has a role in construction of the T4SS conjugative pore. Using antisera to the F‐T4SS proteins we demonstrate that traF and trbB mutations affect the stability of the T4SS complex, particularly TraH and TraV.