Table 2.

Glycan binding residues of H1N1 HAs

H1N1 Strains	Cluster 1				Cluster 2					Cluster 3		Cluster 4						Cluster 5
	136	138	226	137	153	155	194	183	145	222	225	190	189	187	186	219	227	192	193	156	159	196
SolIs_3_06	S	S	Q	A	W	T	L	H	S	K	D	D	G	N	P	K	E	R	A	G	G	H
Bris_59_07	S	S	Q	A	W	T	L	H	S	K	D	D	G	N	P	K	E	K	A	G	G	H
NewCal_20_	S	S	Q	A	W	T	L	H	S	K	D	N	G	N	P	K	E	R	A	G	G	H
TX_36_91	T	S	Q	T	W	T	I	H	S	K	D	D	R	N	S	K	E	R	A	E	G	H
SC18	T	A	Q	A	W	T	L	H	S	K	D	D	T	T	P	A	A	Q	S	K	S	Q
TX/15	T	A	Q	A	W	V	L	H	K	K	D	D	A	T	S	I	E	Q	S	K	N	Q
MX/4482	T	A	Q	A	W	V	L	H	K	K	D	D	A	T	S	I	E	Q	S	K	N	Q
CA/04	T	A	Q	A	W	V	L	H	K	K	D	D	A	T	S	I	E	Q	S	K	N	Q
	Neu5Ac-1									Gal-2		GlcNAc-3						Gal-4, Glc-5, …

The residues are organized into network forming clusters. The sugar unit (numbered as shown in Figure 3), which makes contact with the clusters, is shown in the last row. The unique amino acids in 2009 H1N1 HAs are highlighted in red. The key for the virus strains SolIS_3_06 (A/Solomon Islands/3/06); Bris_59_07 (A/Brisbane/59/07); NewCal_20_99 (A/New Caledonia/20/99); TX_36_91 (A/Texas/36/91).