Table 1.
HA receptor-binding residues of selected H1 influenza viruses
| Strain* | HA receptor-binding
residues†
|
|||||
|---|---|---|---|---|---|---|
| 77 | 138 | 186 | 190 | 194 | 225 | |
| Avian strains | D | A | P | E | L | G |
| Sw/Germany/91 | D | A | P | D | L | G |
| 1918 strains | D | A | P | D | L | G (1), D (2)‡ |
| Sw/Iowa/31 | D | A | P | D | L | G |
| Sw/Illinois/63 | E | A | P | D | L | G |
| PR/8/34 | D | A | S | D | I | D |
| Ft. Monmouth/47 | E | S | S | D | I | G |
| USSR/77 | E | S | S | D | I | G |
*
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.