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Substrate recognition by the bacterial type II secretion system: more than a simple interaction
Author(s) -
Pineau Camille,
Guschinskaya Natalia,
Robert Xavier,
Gouet Patrice,
Ballut Lionel,
Shevchik Vladimir E.
Publication year - 2014
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 - 10.1111/mmi.12744
Subject(s) - periplasmic space , biology , secretion , bacterial outer membrane , pdz domain , signal peptide , cell envelope , microbiology and biotechnology , biochemistry , peptide sequence , escherichia coli , gene
Summary Type II secretion system ( T 2 SS ) is a multiprotein trans‐envelope complex that translocates fully folded proteins through the outer membrane of G ram‐negative bacteria. Although T 2 SS is extensively studied in several bacteria pathogenic for humans, animals and plants, the molecular basis for exoprotein recruitment by this secretion machine as well as the underlying targeting motifs remain unknown. To address this question, we used bacterial two‐hybrid, surface plasmon resonance, in vivo site‐specific photo‐cross‐linking approaches and functional analyses. We showed that the fibronectin‐like Fn 3 domain of exoprotein PelI from D ickeya dadantii interacts with four periplasmic domains of the T 2 SS components GspD and GspC . The interaction between exoprotein and the GspC PDZ domain is positively modulated by the GspD N 1 domain, suggesting that exoprotein secretion is driven by a succession of synergistic interactions. We found that an exposed 9‐residue‐long loop region of PelI interacts with the GspC PDZ domain. This loop acts as a specific secretion signal that controls exoprotein recruitment by the T 2 SS . Concerted in silico and in vivo approaches reveal the occurrence of equivalent secretion motifs in other exoproteins, suggesting a plausible general mechanism of exoprotein recruitment by the T 2 SS .