Electrostatic interactions play a minor role in the binding of ExoS to 14-3-3 proteins

Lubna Yasmin, Jeffrey L. Veesenmeyer, Maureen H. Diaz, Matthew S. Francis, Christian Ottmann, Ruth H. Palmer, Alan R. Hauser, Bengt Hallberg*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

10 Scopus citations


14-3-3 proteins belong to a family of conserved molecules expressed in all eukaryotic cells that play an important role in a multitude of signalling pathways. 14-3-3 proteins bind either to phosphoserine/phosphothreonine residues or to sequence-specific non-phosphorylated motifs in more than 200 interaction partners [Pozuelo Rubio, Geraghty, Wong, Wood, Campbell, Morrice and Mackintosh (2004) Biochem. J. 379, 395-408]. These interactions result in cell-cycle regulation, apoptosis, stress responses, cell metabolism and malignant transformation. One example of a phosphorylation-independent interaction is the binding of 14-3-3 to ExoS (exoenzyme S), a bacterial ADP-ribosyltransferase toxin of Pseudomonas aeruginosa. In the present study, we have utilized additional biochemical and infection analyses to define further the structural basis of the interaction between ExoS and 14-3-3. An ExoS leucinesubstitution mutant dramatically reduced the interaction potential with 14-3-3 suggesting that Leu422, Leu423, Leu426 and Leu 428 of ExoS are important for its interaction with 14-3-3, its enzymatic activity and cytotoxicity. However, ExoS substitution mutants of residues that interact with 14-3-3 through an electrostatic interaction, such as Ser416, His418, Asp424 and Asp427, showed no reduction in their interaction potential with 14-3-3. These ExoS substitution mutants were also as aggressive as wild-type ExoS at inducing cell death and to modify endogenous ExoS target within the cell. In conclusion, electrostatic interaction between ExoS and 14-3-3 via polar residues (Ser 416, His418, Asp424 and Asp427) appears to be of secondary importance. Thus the interaction between the 'roof' of the groove of 14-3-3 and ExoS relies more on hydrophobic interaction forces, which probably contributes to induce cell death after ExoS infection and activation.

Original languageEnglish (US)
Pages (from-to)217-224
Number of pages8
JournalBiochemical Journal
Issue number2
StatePublished - Apr 15 2010


  • 14-3-3 protein
  • ADP-ribosyltransferase
  • Akt/protein kinase B (PKB)
  • Exoenzyme S (ExoS)
  • Pseudomonas aeruginosa
  • Ras

ASJC Scopus subject areas

  • Molecular Biology
  • Biochemistry
  • Cell Biology


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