title: Investigation of the binding and cleavage characteristics of N1 neuraminidases from avian, seasonal, and pandemic influenza viruses using saturation transfer difference nuclear magnetic resonance.
abstract: OBJECTIVE
  The main function of influenza neuraminidase (NA) involves enzymatic cleavage of sialic acid from the surface of host cells resulting in the release of the newly produced virions from infected cells, as well as aiding the movement of virions through sialylated mucus present in the respiratory tract. However, there has previously been little information on the binding affinity of different forms of sialylated glycan with NA. Our objectives were then to investigate both sialic acid binding and cleavage of neuraminidase at an atomic resolution level.
  
  
  METHODS
  Nuclear magnetic resonance (NMR) spectroscopy was used to investigate pH and temperature effects on binding and cleavage as well as to interrogate the selectivity of human-like or avian-like receptors for influenza neuraminidase N1 derived from a range of different influenza virus strains including human seasonal H1N1, H1N1pdm09 and avian H5N1.
  
  
  RESULTS
  We demonstrated that an acidic pH and physiological temperature are required for efficient NA enzymatic activity; however a change in the pH had a minimum effect on the NA-sialic acid binding affinity. Our data comparing α-2,3- and α-2,6-sialyllactose indicated that the variation in neuraminidase activity on different ligands correlated with a change in binding affinity. Epitope mapping of the sialylglycans interacting with NAs from different viral origin showed different binding profiles suggesting that different binding conformations were adopted.
  
  
  CONCLUSIONS
  The data presented in this study demonstrated that physicochemical conditions (pH in particular) could affect the NA enzymatic activity with minor effect on ligand binding. NA cleavage specificity seemed to be associated with a difference in binding affinity to different ligands, suggesting a relationship between the two events. These findings have implications regarding the replication cycle of influenza infection in the host where different sialidase activities would influence penetration through the respiratory mucin barrier and the release of the newly generated virus from the infected cells.
authors.affiliation: HKU-Pasteur Research Centre, Hong Kong SAR, China.
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Garcia
authors.forename: Jimmy C C
authors.initials: JC
authors.lastname: Lai
authors.forename: Thomas
authors.initials: T
authors.lastname: Haselhorst
authors.forename: Ka Tim
authors.initials: KT
authors.lastname: Choy
authors.forename: Hui-Ling
authors.initials: HL
authors.lastname: Yen
authors.forename: Joseph S M
authors.initials: JS
authors.lastname: Peiris
authors.forename: Mark
authors.initials: M
authors.lastname: von Itzstein
authors.forename: John M
authors.initials: JM
authors.lastname: Nicholls
mesh_terms: D000818:Animals; D001717:Birds; D004795:Enzyme Stability; D006801:Humans; D006863:Hydrogen-Ion Concentration; D053118:Influenza A Virus, H1N1 Subtype / Q000201:enzymology* / Q000302:isolation & purification; D053124:Influenza A Virus, H5N1 Subtype / Q000201:enzymology* / Q000302:isolation & purification; D005585:Influenza in Birds / Q000821:virology; D007251:Influenza, Human / Q000821:virology; D009682:Magnetic Resonance Spectroscopy; D009439:Neuraminidase / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D012794:Sialic Acids / Q000378:metabolism*; D013379:Substrate Specificity; D013696:Temperature; D014764:Viral Proteins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D012794:Sialic Acids; D014764:Viral Proteins; C487630:NA protein, influenza A virus; D009439:Neuraminidase
keywords: Epitope mapping; influenza; neuraminidase; nuclear magnetic resonance; receptor interaction; saturation transfer difference