title: Interfacial residues of SpcS chaperone affects binding of effector toxin ExoT in Pseudomonas aeruginosa: novel insights from structural and computational studies.
abstract: ExoT belongs to the family of type 3 secretion system (T3SS) effector toxins in Pseudomonas aeruginosa, known to be one of the major virulence determinant toxins that cause chronic and acute infections in immuno-compromised individuals, burn victims and cystic fibrosis patients. Here, we report the X-ray crystal structure of the amino terminal fragment of effector toxin ExoT, in complex with full-length homodimeric chaperone SpcS at 2.1 Å resolution. The full-length dimeric chaperone SpcS has the conserved α-β-β-β-α-β-β-α fold of class I chaperones, the characteristic hydrophobic patches for binding effector proteins and a conserved polar cavity at the dimeric interface. The stable crystallized amino terminal fragment of ExoT consists of a chaperone binding domain and a membrane localization domain that wraps around the dimeric chaperone. Site-directed mutagenesis experiments and a molecular dynamics study complement each other in revealing Asn65, Phe67 and Trp88 as critical dimeric interfacial residues that can strongly influence the effector-chaperone interactions.
authors.affiliation: Department of Structural Biology and Bioinformatics, Indian Institute of Chemical Biology, Kolkata, India.
authors.forename: Supratim
authors.initials: S
authors.lastname: Dey
authors.forename: Saumen
authors.initials: S
authors.lastname: Datta
mesh_terms: D036002:ADP Ribose Transferases / Q000378:metabolism*; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D011485:Protein Binding; D011550:Pseudomonas aeruginosa / Q000378:metabolism*
chemical_list: C477521:ExoT protein, Pseudomonas aeruginosa; D020690:GTPase-Activating Proteins; D036002:ADP Ribose Transferases
keywords: chaperone binding domain; effector-chaperone complex; hot spots; membrane localization domain; molecular dynamics; type III secretion system