The O-antigenic repeating units of the Salmonella cell surface lipopolysaccharides (serotypes A, B and D1) serve as receptors for phage P22. This initial binding step is mediated by the tailspike protein (TSP), which is present in six copies on the base plate of the phage. In addition to the binding activity, TSP also displays a low endoglycolytic activity, cleaving the α(1,3)-O-glycosidic bond between rhamnose and galactose of the O-antigenic repeats. The crystal structure of TSP in complex with receptor fragments allowed to identify the receptor binding site for the octasaccharide product of the enzymatic action of TSP on delipidated LPS and the active site consisting of Asp392, Asp395 and Glu359. The structure comprises a large right-handed parallel beta-helix of 13 turns. These fold independently in the trimer, whereas the N-terminus forms a cap-like structure and the C-terminal parts of the three polypeptide strands merge to a single common domain. In addition, TSP has served as model system for the folding of large, multisubunit proteins. Its folding pathway is influenced by a large number of point mutations, classified as lethal, temperature sensitive or general suppressor mutations, which influence the partitioning between aggregation and the productive folding pathway.
O-antigen, Salmonella, crystal structure, endoglycosidase, X-ray crystallography, phage mutants, protein folding, receptor binding, β-helix, virus proyein
NCBI PubMed ID: 9165091Journal NLM ID: 9700112Publisher: Berlin: Walter De Gruyter
Institutions: Max-Planck-Institut für Biochemie, Abteilung für Strukturforschung, Martinsried, Germany, Institut für Biophysik und Physikalische Biochemie, Universitat Regensburg, D-93040 Regensburg, Germany, Department of Immunology, Pathology and Infectious Diseases Division of Clinical Bacteriology, Huddinge University Hospital, Karolinska Institutet, Huddinge, Sweden
Methods: X-ray
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