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Phosphorylation‐independent interaction between 14‐3‐3 and exoenzyme S: from structure to pathogenesis
Author(s) -
Ottmann Christian,
Yasmin Lubna,
Weyand Michael,
Veesenmeyer Jeffrey L,
Diaz Maureen H,
Palmer Ruth H,
Francis Matthew S,
Hauser Alan R,
Wittinghofer Alfred,
Hallberg Bengt
Publication year - 2007
Publication title -
the embo journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 7.484
H-Index - 392
eISSN - 1460-2075
pISSN - 0261-4189
DOI - 10.1038/sj.emboj.7601530
Subject(s) - biology , phosphorylation , phosphoserine , microbiology and biotechnology , binding site , biochemistry , plasma protein binding , virulence , signal transducing adaptor protein , protein structure , biophysics , serine , gene
14‐3‐3 proteins are phosphoserine/phosphothreonine‐recognizing adapter proteins that regulate the activity of a vast array of targets. There are also examples of 14‐3‐3 proteins binding their targets via unphosphorylated motifs. Here we present a structural and biological investigation of the phosphorylation‐independent interaction between 14‐3‐3 and exoenzyme S (ExoS), an ADP‐ribosyltransferase toxin of Pseudomonas aeruginosa . ExoS binds to 14‐3‐3 in a novel binding mode mostly relying on hydrophobic contacts. The 1.5 Å crystal structure is supported by cytotoxicity analysis, which reveals that substitution of the corresponding hydrophobic residues significantly weakens the ability of ExoS to modify the endogenous targets RAS/RAP1 and to induce cell death. Furthermore, mutation of key residues within the ExoS binding site for 14‐3‐3 impairs virulence in a mouse pneumonia model. In conclusion, we show that ExoS binds 14‐3‐3 in a novel reversed orientation that is primarily dependent on hydrophobic residues. This interaction is phosphorylation independent and is required for the function of ExoS.