H1 and H7 influenza haemagglutinin structures extend a structural classification of haemagglutinin subtypes

Virology. 2004 Aug 1;325(2):287-96. doi: 10.1016/j.virol.2004.04.040.


Comparing the structures of H3, H5 and H9 subtype haemagglutinins, we deduced a structural basis for including all 15 influenza subtypes in four clades. H3, H5 and H9 represent three of these clades; we now report the structure of an H7 HA as a representative of the fourth clade. We confirm the structure of the turn at the N-terminus of the conserved central alpha-helix of HA2, and the combination of ionisable residues near the "fusion peptide" as clade-specific features. We compare the structures of three H1 HAs with H5 HA in the same clade, to refine our previous classification and we confirm the division of the clades into two groups of two. We also show the roles of carbohydrate side chains in the esterase-fusion domain boundaries in the formation of clade-specific structural markers.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Carbohydrates / chemistry
  • Crystallography, X-Ray
  • Hemagglutinin Glycoproteins, Influenza Virus / chemistry*
  • Hemagglutinin Glycoproteins, Influenza Virus / classification*
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics
  • Humans
  • Influenza A virus / chemistry*
  • Influenza A virus / classification*
  • Influenza A virus / genetics
  • Models, Molecular
  • Molecular Sequence Data
  • Phylogeny
  • Protein Structure, Quaternary
  • Protein Structure, Tertiary
  • Sequence Homology, Amino Acid


  • Carbohydrates
  • Hemagglutinin Glycoproteins, Influenza Virus
  • hemagglutinin, avian influenza A virus
  • hemagglutinin, human influenza A virus

Associated data

  • PDB/1RU7
  • PDB/1RUY
  • PDB/1RUZ
  • PDB/1RV0
  • PDB/1RVT
  • PDB/1RVX
  • PDB/1RVZ
  • PDB/1TI8