Table 1

HA receptor-binding residues of selected H1 influenza viruses

Strain*HA receptor-binding residues
77138186190194225
Avian strainsDAPELG
Sw/Germany/91DAPDLG
1918 strainsDAPDLG (1), D (2)
Sw/Iowa/31DAPDLG
Sw/Illinois/63EAPDLG
PR/8/34DASDID
Ft. Monmouth/47ESSDIG
USSR/77ESSDIG
  • * Selected strains are shown. These six amino acid positions are unvaried in all avian HAs (23). The 1918 strains are South Carolina/1/18, New York/1/18, and Brevig Mission/1/18. Other sequences were obtained from GenBank. Complete strain names are listed in Materials and Methods and/or ref. 2

  • Amino acid numbering is aligned to the H3 influenza HA (27). 

  • The 1918 strains differ at this site. New York/1/18 has a glycine residue (G), whereas both South Carolina/1/18 and Brevig Mission/1/18 have an aspartic acid (D) at this site.