4xkv

Tailspike protein mutant D339N of E. coli bacteriophage HK620

spinqualitylabelsall models 4xkv, resolution 2.10Å Show:Asymmetric Unit Biological Assembly Drag the structure with the mouse to rotate   Export Animated Image   Print3D Structural highlights 4xkv is a 1 chain structure with sequence from Bphk6. Full crystallographic information is available from OCA. For a guided tour on the structure components use FirstGlance. Ligands: FMT, NA, TRS Related: 2vij, 2vjj, 2x6w, 2x6x, 2x6y, 2x85, 4avz, 4pat Resources: FirstGlance, OCA, PDBe, RCSB, PDBsum, ProSAT Publication Abstract from PubMed Bacteriophage HK620 recognizes and cleaves the Oantigen polysaccharide of E. coli serogroup O18A1 with its tailspike protein (TSP). HK620TSP binds hexasaccharide fragments with low affinity, but single amino acid exchanges generated a set of high-affinity mutants with submicromolar dissociation constants. Isothermal titration calorimetry showed that only small amounts of heat were released upon complex formation via a large number of direct and solvent mediated hydrogen bonds between carbohydrate and protein. At room temperature association was both enthalpy- and entropy-driven emphasizing major solvent rearrangements upon complex formation. Crystal structure analysis showed identical protein and sugar conformers in the TSP complexes regardless of their hexasaccharide affinity. Only in one case a TSP mutant bound a different hexasaccharide conformer. The extended sugar binding site could be dissected in two regions: Firstly, a hydrophobic pocket at the reducing end with minor affinity contributions. Access to this site could be blocked by a single aspartate to asparagine exchange without major loss in hexasaccharide affinity. Secondly, a region where specific exchange of glutamate for glutamine created a site for an additional water molecule. Side chain rearrangements upon sugar binding led to desolvation and additional hydrogen bonding which define this region of the binding site as the high affinity scaffold. Single amino acid exchange in bacteriophage HK620 tailspike protein results in thousand-fold increase of its oligosaccharide affinity.,Broeker NK, Gohlke U, Muller JJ, Uetrecht C, Heinemann U, Seckler R, Barbirz S Glycobiology. 2012 Aug 24. PMID:22923442 From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.

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