title: Crystallographic detection of a second ligand binding site in influenza virus hemagglutinin.
abstract: X-ray crystal structures have been determined for several complexes between influenza virus hemagglutinin and derivatives of its cell-surface receptor, sialic acid (Neu5Ac). Difference electron density maps establish the existence of a second binding site in addition to the primary site characterized previously. Three compounds bind to both sites: Neu5Ac(alpha 2-3)Gal(beta 1-4)Glc [(alpha 2-3)sialyllactose], alpha-2-O-(4'-benzylamidocarboxybutyl)-5-N-acetylneuraminic acid, and alpha-2-O-(4'-methylamidocarboxybutyl)-5-N-acetylneuraminic acid; and four other compounds bind only to the primary site: Neu5Ac(alpha 2-6)Gal(beta 1-4)Glc [(alpha 2-6)sialyllactose], alpha-2-O-methyl-5-N-acetylneuraminic acid, 4-]-acetyl-alpha-2-O-methyl-5-N-acetylneuraminic acid, and 9-amino-9-deoxy-alpha-2-O-methyl-5-N-acetylneuraminic acid. The maps also extend earlier results by showing the location of all three sugar residues of (alpha 2-3)sialyllactose in the primary binding site. The affinity of (alpha 2-3)sialyllactose for the second site was estimated by collecting x-ray diffraction data at various ligand concentrations and was found to be at least four times weaker than its affinity for the primary site. Although it is not yet known whether the second binding site participates in the infection process, it nevertheless offers a potential target for the design of antiviral drugs.
authors.affiliation: Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, MA 02138.
authors.forename: N K
authors.initials: NK
authors.lastname: Sauter
authors.forename: G D
authors.initials: GD
authors.lastname: Glick
authors.forename: R L
authors.initials: RL
authors.lastname: Crowther
authors.forename: S J
authors.initials: SJ
authors.lastname: Park
authors.forename: M B
authors.initials: MB
authors.lastname: Eisen
authors.forename: J J
authors.initials: JJ
authors.lastname: Skehel
authors.forename: J R
authors.initials: JR
authors.lastname: Knowles
authors.forename: D C
authors.initials: DC
authors.lastname: Wiley
mesh_terms: D001665:Binding Sites; D003461:Crystallography; D006389:Hemagglutinins, Viral / Q000378:metabolism / Q000648:ultrastructure*; D006863:Hydrogen-Ion Concentration; D008024:Ligands; D008561:Membrane Fusion; D008958:Models, Molecular; D019158:N-Acetylneuraminic Acid; D009975:Orthomyxoviridae / Q000378:metabolism*; D011991:Receptors, Virus / Q000378:metabolism; D012794:Sialic Acids / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D006389:Hemagglutinins, Viral; D008024:Ligands; D011991:Receptors, Virus; D012794:Sialic Acids; D019158:N-Acetylneuraminic Acid