Table 1.

Atomic contacts between sialosides (LSTa, α2,3, and LSTc α2,6) and H5 (avian), H9 (swine), and H3 (human) subtype influenza virus HAs

	H3 human		H5 avian		H9 swine
	2,3	2,6	2,3	2,6	2,3	2,6
98Y	Y-Sia1	Y-Sia1	Y-Sia1	Y-Sia1	Y-Sia1	Y-Sia1
131						S-Glc5
133						S-Glc5
133a			S-Sia1	S-Sia1
134	G-Sia1		G-Sia1	G-Sia1	G-Sia1	G-Sia1, G-Glc5
135mc	G-Sia1	G-Sia1	V-Sia1	V-Sia1	T-Sia1	T-Sia1, T-Glc5
136S	S-Sia1	S-Sia1	S-Sia1	S-Sia1	S-Sia1	S-Sia1
137mc	N-Sia1	N-Sia1	S-Sia1	S-Sia1	K-Sia1, K-Gal2	K-Sia1
153W	W-Sia1	W-Sia1	W-Sia1	W-Sia1	W-Sia1	W-Sia1
155	T-Sia1	T-Sia1	I-Sia1	I-Sia1	T-Sia1	T-Sia1, T-Gal4
156		K-Glc5				Q-Gal4
158		G-Glc5
165	CHO-NAG3
183	H-Sia1	H-Sia1	H-Sia1	H-Sia1
186			N-Sia1		P-Sia1	P-Sia1
189	Q-Gal4
190	E-Sia1	E-Sia1	E-Sia1, E-Gal2	E-Sia1	V-Sia1	V-Sia1, V-NAG3
193		S-Glc5				N-NAG3, N-Gal4
194L	L-Sia1	L-Sia1	L-Sia1	L-Sia1	L-Sia1	L-Sia1, L-Gal4
222	W-Gal2, W-NAG3
225	G-Gal2				G-Gal2
226	L-Sia1, L-Gal2	L-Sia1, L-Gal2	Q-Sia1, Q-Gal2	Q-Sia1	L-Sia1, L-Gal2	L-Sia1, L-Gal2
228	S-Sia1	S-Sia1	H2O-Sia1	H2O-Sia1	H2O-Sia1	H2O-Sia1
Receptor
Sia1		NAG3				NAG3, Gal4, Glc5
Gal2		NAG3

Conserved interactions are underlined. Contacts with hydrogen bonds are in bold. The first column is the sequence according to H3 (X31) numbering. The first elements in each entry represent the amino acid at the corresponding position. Intramolecular interactions within the receptor are listed at the bottom of the table. At position 165 in H3/LSTa, the interaction is between NAG3 and the N linked CHO at Asn-165 across the trimeric interface. At position 228 in H5 and H9, a water molecule mediates the hydrogen bond from Sia1 and Gly-228.