title: Crystal structure and oligomeric state of the RetS signaling kinase sensory domain.
abstract: 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 A 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 nM, a result with interesting implications for our understanding of the underlying signaling mechanism.
authors.affiliation: Department of Biological Sciences, Life Science I, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24060, USA.
authors.forename: Xing
authors.initials: X
authors.lastname: Jing
authors.forename: Jessica
authors.initials: J
authors.lastname: Jaw
authors.forename: Howard H
authors.initials: HH
authors.lastname: Robinson
authors.forename: Florian David
authors.initials: FD
authors.lastname: Schubot
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008969:Molecular Sequence Data; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D011550:Pseudomonas aeruginosa / Q000201:enzymology; D016415:Sequence Alignment; D015398:Signal Transduction
chemical_list: D001426:Bacterial Proteins; C507835:RetS protein, Pseudomonas aeruginosa