2X6X

Tailspike protein mutant D339N of E.coli bacteriophage HK620 in complex with hexasaccharide

Summary for 2X6X

• Entry DOI: 10.2210/pdb2x6x/pdb
• Related: 2VJI 2VJJ 2X6W 2X6Y 2X85
• Descriptor: TAILSPIKE PROTEIN HK620, alpha-L-rhamnopyranose-(1-6)-alpha-D-glucopyranose-(1-4)-[2-acetamido-2-deoxy-beta-D-glucopyranose-(1-3)]alpha-D-galactopyranose, 2-AMINO-2-HYDROXYMETHYL-PROPANE-1,3-DIOL, ... (4 entities in total)
• Functional Keywords: hydrolase, viral protein
• Biological source: SALMONELLA PHAGE HK620
• Total number of polymer chains: 1
• Total formula weight: 65518.14

Authors

Lorenzen, N.K.,Mueller, J.J.,Heinemann, U.,Seckler, R.,Barbirz, S. (deposition date: 2010-02-22, release date: 2011-03-02, Last modification date: 2023-12-20)

Primary citation

Broeker, N.K.,Gohlke, U.,Muller, J.J.,Uetrecht, C.,Heinemann, U.,Seckler, R.,Barbirz, S.
Single Amino Acid Exchange in Bacteriophage Hk620 Tailspike Protein Results in Thousand-Fold Increase of its Oligosaccharide Affinity.
Glycobiology, 23:59-, 2013

PubMed Abstract: Bacteriophage HK620 recognizes and cleaves the O-antigen polysaccharide of Escherichia 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: first, 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. Second, a region where the 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.

PubMed: 22923442
DOI: 10.1093/GLYCOB/CWS126

Experimental method

X-RAY DIFFRACTION (1.48 Å)