title: Carbohydrate binding of Salmonella phage P22 tailspike protein and its role during host cell infection.
abstract: TSPs (tailspike proteins) are essential infection organelles of bacteriophage P22. Upon infection, P22TSP binds to and cleaves the O-antigen moiety of the LPS (lipopolysaccharide) of its Salmonella host. To elucidate the role of TSP during infection, we have studied binding to oligosaccharides and polysaccharides of Salmonella enterica Typhimurium and Enteritidis in vitro. P22TSP is a trimeric β-helical protein with a carbohydrate-binding site on each subunit. Octasaccharide O-antigen fragments bind to P22TSP with micromolar dissociation constants. Moreover, P22TSP is an endorhamnosidase and cleaves the host O-antigen. Catalytic residues lie at the periphery of the high-affinity binding site, which enables unproductive binding modes, resulting in slow hydrolysis. However, the role of this hydrolysis function during infection remains unclear. Binding of polysaccharide to P22TSP is of high avidity with slow dissociation rates when compared with oligosaccharides. In vivo, the infection of Salmonella with phage P22 can be completely inhibited by the addition of LPS, indicating that binding of phage to its host via TSP is an essential step for infection.
authors.affiliation: Physikalische Biochemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, 14476 Golm, Germany.
authors.forename: Dorothee
authors.initials: D
authors.lastname: Andres
authors.forename: Ulrich
authors.initials: U
authors.lastname: Baxa
authors.forename: Christin
authors.initials: C
authors.lastname: Hanke
authors.forename: Robert
authors.initials: R
authors.lastname: Seckler
authors.forename: Stefanie
authors.initials: S
authors.lastname: Barbirz
mesh_terms: D017100:Bacteriophage P22 / Q000378:metabolism* / Q000472:pathogenicity*; D006026:Glycoside Hydrolases; D011485:Protein Binding; D017433:Protein Structure, Secondary; D012475:Salmonella / Q000821:virology*; D017376:Viral Tail Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D017376:Viral Tail Proteins; D006026:Glycoside Hydrolases; C083268:tailspike protein, bacteriophage