We present a computational study on the conformational characteristics of Serotype Y O-Antigen polysaccharide fragments of the Gram-negative bacterium Shigella flexneri in solution [1] and bound to the tailspike protein (TSP) of bacteriophage Sf6. The molecular models of the protein-carbohydrate complexes are in good agreement with X-ray structures of TSP co-crystallized with tetrasaccharide fragments on the wild type [2], and octasaccharides with inactive mutants. The bound octasacharide conformer resembles the dominant one in solution. In addition, an investigation has been carried out on how longer O-Antigen fragments could be accommodated at the binding site such as to correctly place the Rhap a(1-3) linkage at the active carboxy-residues prior to cleavage. We find that significant excursions from the low-energy equilibrium conformations must occur in order to avoid steric clashes or inconvenient placement, indicating that conformational selection should play a significant role in the interaction of O-Antigen with TSP.[1] Kang, Y.; Barbirz, S.; Lipowsky, R. and Santer, M. Conformational Diversity of O-Antigen Polysaccharides of the Gram-negative Bacterium Shigella flexneri Serotype Y. J. Phys. Chem. B, Doi:  10.1021/jp4111713 (2014)[2] M�ller, J. J.; Barbirz, S.; Heinle, K.; Freiberg, A.; Seckler R.; Heinemann, U. An Intersubunit Active Site between Supercoiled Parallel � Helices in the Trimeric Tailspike Endorhamnosidase of Shigella flexneri Phage Sf6. Structure 2008 , 16, 766-775.

Molecular dynamics study on the interaction of O-antigen polysaccharides of the gram-negative bacterium <i>Shigella flexneri</i> with the tail-spike-protein of bacteriophage Sf6

248th National Meeting (2014)

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Molecular dynamics study on the interaction of O-antigen polysaccharides of the gram-negative bacterium Shigella flexneri with the tail-spike-protein of bacteriophage Sf6