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Crystal structure and oligomeric state of the RetS signaling kinase sensory domain
Author(s) -
Jing Xing,
Jaw Jessica,
Robinson Howard H.,
Schubot Florian David
Publication year - 2010
Publication title -
proteins: structure, function, and bioinformatics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.699
H-Index - 191
eISSN - 1097-0134
pISSN - 0887-3585
DOI - 10.1002/prot.22679
Subject(s) - autophosphorylation , periplasmic space , protein kinase domain , biofilm , signal transduction , microbiology and biotechnology , biology , biogenesis , phosphorylation , histidine kinase , protein structure , chemistry , protein kinase a , biochemistry , genetics , mutant , gene , bacteria , escherichia coli
The opportunistic pathogen Pseudomonas aeruginosa may cause both acute and chronic‐persistent infections in predisposed individuals. Acute infections require the presence of a functional type III secretion system (T3SS), whereas chronic P. aeruginosa infections are characterized by the formation of drug‐resistant biofilms. The T3SS and biofilm formation are reciprocally regulated by the signaling kinases LadS, RetS, and GacS. RetS downregulates biofilm formation and upregulates expression of the T3SS through a unique mechanism. RetS forms a heterodimeric complex with GacS and thus prevents GacS autophosphorylation and downstream signaling. The signals that regulate RetS are not known but RetS possesses a distinctive periplasmic sensor domain that is believed to serve as receptor for the regulatory ligand. We have determined the crystal structure of the RetS sensory domain at 2.0 Å resolution. The structure closely resembles those of carbohydrate binding modules of other proteins, suggesting that the elusive ligands are likely carbohydrate moieties. In addition to the conserved beta‐sandwich structure, the sensory domain features two alpha helices which create a unique surface topology. Protein–protein crosslinking and fluorescence energy transfer experiments also revealed that the sensory domain dimerizes with a dissociation constant of K d = 580 ± 50 n M , a result with interesting implications for our understanding of the underlying signaling mechanism. Proteins 2010. © 2009 Wiley‐Liss, Inc.