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VirE2, a Type IV secretion substrate, interacts with the VirD4 transfer protein at cell poles of Agrobacterium tumefaciens
Author(s) -
Atmakuri Krishnamohan,
Ding Zhiyong,
Christie Peter J.
Publication year - 2003
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2003.03669.x
Subject(s) - biology , agrobacterium tumefaciens , bimolecular fluorescence complementation , effector , secretion , bacterial conjugation , periplasmic space , chaperone (clinical) , peptidylprolyl isomerase , microbiology and biotechnology , agrobacterium , dna , genetics , gene , biochemistry , transformation (genetics) , escherichia coli , plasmid , pathology , isomerase , medicine
Summary Agrobacterium tumefaciens transfers oncogenic DNA and effector proteins to plant cells during the course of infection. Substrate translocation across the bacterial cell envelope is mediated by a type IV secretion (TFS) system composed of the VirB proteins, as well as VirD4, a member of a large family of inner membrane proteins implicated in the coupling of DNA transfer intermediates to the secretion machine. In this study, we demonstrate with novel cytological screens – a two‐hybrid (C2H) assay and bimolecular fluorescence complementation (BiFC) – and by immunoprecipitation of chemically cross‐linked protein complexes that the VirE2 effector protein interacts directly with the VirD4 coupling protein at cell poles of A. tumefaciens . Analyses of truncation derivatives showed that VirE2 interacts via its C terminus with VirD4, and, further, an NH 2 ‐terminal membrane‐spanning domain of VirD4 is dispensable for complex formation. VirE2 interacts with VirD4 independently of the virB ‐encoded transfer machine and T pilus, the putative periplasmic chaperones AcvB and VirJ, and the T‐DNA transfer intermediate. Finally, VirE2 is recruited to polar‐localized VirD4 as a complex with its stabilizing secretion chaperone VirE1, yet the effector–coupling protein interaction is not dependent on chaperone binding. Together, our findings establish for the first time that a protein substrate of a type IV secretion system is recruited to a member of the coupling protein superfamily.