TY - JOUR
T1 - Genetically distinct pathways guide effector export through the type VI secretion system
AU - Whitney, John C.
AU - Beck, Christina M.
AU - Goo, Young Ah
AU - Russell, Alistair B.
AU - Harding, Brittany N.
AU - De Leon, Justin A.
AU - Cunningham, David A.
AU - Tran, Bao Q.
AU - Low, David A.
AU - Goodlett, David R.
AU - Hayes, Christopher S.
AU - Mougous, Joseph D.
PY - 2014/5
Y1 - 2014/5
N2 - Summary: Bacterial secretion systems often employ molecular chaperones to recognize and facilitate export of their substrates. Recent work demonstrated that a secreted component of the type VI secretion system (T6SS), haemolysin co-regulated protein (Hcp), binds directly to effectors, enhancing their stability in the bacterial cytoplasm. Herein, we describe a quantitative cellular proteomics screen for T6S substrates that exploits this chaperone-like quality of Hcp. Application of this approach to the Hcp secretion island I-encoded T6SS (H1-T6SS) of Pseudomonas aeruginosa led to the identification of a novel effector protein, termed Tse4 (type VI secretion exported 4), subsequently shown to act as a potent intra-specific H1-T6SS-delivered antibacterial toxin. Interestingly, our screen failed to identify two predicted H1-T6SS effectors, Tse5 and Tse6, which differ from Hcp-stabilized substrates by the presence of toxin-associated PAAR-repeat motifs and genetic linkage to members of the valine-glycine repeat protein G (vgrG) genes. Genetic studies further distinguished these two groups of effectors: Hcp-stabilized effectors were found to display redundancy in interbacterial competition with respect to the requirement for the two H1-T6SS-exported VgrG proteins, whereas Tse5 and Tse6 delivery strictly required a cognate VgrG. Together, we propose that interaction with either VgrG or Hcp defines distinct pathways for T6S effector export.
AB - Summary: Bacterial secretion systems often employ molecular chaperones to recognize and facilitate export of their substrates. Recent work demonstrated that a secreted component of the type VI secretion system (T6SS), haemolysin co-regulated protein (Hcp), binds directly to effectors, enhancing their stability in the bacterial cytoplasm. Herein, we describe a quantitative cellular proteomics screen for T6S substrates that exploits this chaperone-like quality of Hcp. Application of this approach to the Hcp secretion island I-encoded T6SS (H1-T6SS) of Pseudomonas aeruginosa led to the identification of a novel effector protein, termed Tse4 (type VI secretion exported 4), subsequently shown to act as a potent intra-specific H1-T6SS-delivered antibacterial toxin. Interestingly, our screen failed to identify two predicted H1-T6SS effectors, Tse5 and Tse6, which differ from Hcp-stabilized substrates by the presence of toxin-associated PAAR-repeat motifs and genetic linkage to members of the valine-glycine repeat protein G (vgrG) genes. Genetic studies further distinguished these two groups of effectors: Hcp-stabilized effectors were found to display redundancy in interbacterial competition with respect to the requirement for the two H1-T6SS-exported VgrG proteins, whereas Tse5 and Tse6 delivery strictly required a cognate VgrG. Together, we propose that interaction with either VgrG or Hcp defines distinct pathways for T6S effector export.
UR - http://www.scopus.com/inward/record.url?scp=84899656771&partnerID=8YFLogxK
U2 - 10.1111/mmi.12571
DO - 10.1111/mmi.12571
M3 - Article
C2 - 24589350
AN - SCOPUS:84899656771
SN - 0950-382X
VL - 92
SP - 529
EP - 542
JO - Molecular Microbiology
JF - Molecular Microbiology
IS - 3
ER -