BINDING OF INFLUENZA VIRUS HEMAGGLUTININ TO ANALOGS OF ITS CELL-SURFACE RECEPTOR, SIALIC ACID: ANALYSIS BY PROTON NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY AND X-RAY CRYSTALLOGRAPHY

DISORDERED RESIDUES WITH LITTLE OR NO VISIBLE ELECTRON DENSITY: CHAIN A: 1 - 8, 326 - 328 B: 58, 172 - 175 CHAIN C: 1 - 8, 328 D: 58, 172 - 175 CHAIN E: 1 - 8, 327 - 328 F: 58, 172 - 175

N-acetyl-beta-D-glucosamine; 2-acetamido-2-deoxy-beta-D-glucose; 2-acetamido-2-deoxy-D-glucose; 2-acetamido-2-deoxy-glucose; N-ACETYL-D-GLUCOSAMINE

Crystallographic Detection of a Second Ligand Binding Site in Influenza Virus Hemagglutinin

The Structure of a Membrane Fusion Mutant of the Influenza Virus Hemagglutinin

Refinement of the Influenza Virus Hemagglutinin by Simulated Annealing

Structure of the Influenza Virus Hemagglutinin Complexed with its Receptor, Sialic Acid

The Refinement of the Hemagglutinin Membrane Glycoprotein of Influenza Virus

Three-Dimensional Structure of an Antigenic Mutant of the Influenza Virus Hemagglutinin

Structure of the Hemagglutinin Membrane Glycoprotein of Influenza Virus at 3 Angstroms Resolution

Structural Identification of the Antibody-Binding Sites of Hong Kong Influenza Hemagglutinin and Their Involvement in Antigenic Variation

Crystallization and X-Ray Diffraction Studies on the Hemagglutinin Glycoprotein from the Membrane of Influenza Virus

QDLPGNDNSTATLCLGHHAVPNGTLVKTITDDQIEVTNATELVQSSSTGKICNNPHRILDGIDCTLIDALLGDPHCDVFQ
NETWDLFVERSKAFSNCYPYDVPDYASLRSLVASSGTLEFITEGFTWTGVTQNGRSNACKRGPGSGFFSRLNWLTKSGST
YPVLNVTMPNNDNFDKLYIWGIHHPSTNQEQTSLYVQASGRVTVSTRRSQQTIIPNIGSRPWVRGLSSRISIYWTIVKPG
DVLVINSNGNLIAPRGYFKMRTGKSSIMRSDAPIDTCISECITPNGSIPNDKPFQNVNKITYGACPKYVKQNTLKLATGM
RNVPEKQT

GLFGAIAGFIENGWEGMIDGWYGFRHQNSEGTGQAADLKSTQAAIDQINGKLNRVIEKTNEKFHQIEKEFSEVEGRIQDL
EKYVEDTKIDLWSYNAELLVALENQHTIDLTDSEMNKLFEKTRRQLRENAEEMGNGCFKIYHKCDNACIESIRNGTYDHD
VYRDEALNNRFQIKG

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

IN THE VIRUS, CHAIN HA1 CONSISTS OF 328 RESIDUES AND CHAIN HA2 CONSISTS OF 220 RESIDUES. HEMAGGLUTININ MAY BE SOLUBILIZED FROM THE VIRAL MEMBRANE BY BROMELAIN DIGESTION, WHICH REMOVES THE C-TERMINAL HYDROPHOBIC (ANCHORING) DOMAIN FROM CHAIN HA2. AFTER BROMELAIN DIGESTION CHAIN HA2 CONSISTS OF 175 RESIDUES, AS PRESENTED IN THIS ENTRY.

IN THIS ENTRY RESIDUE GLY 135 IN CHAINS A, C, AND E HAS BEEN REPLACED BY ARG. THE LIGAND, N-LINKED CARBOHYDRATE, AND WATER MOLECULES ASSOCIATED WITH EACH MONOMER ARE PRESENTED IMMEDIATELY FOLLOWING CHAIN HA2 OF THAT MONOMER AND HAVE BEEN ASSIGNED THE CHAIN INDICATORS G, H, AND I.

THE TRANSFORMATION PRESENTED AS *MTRIX 1* BELOW WILL YIELD APPROXIMATE COORDINATES FOR MONOMER 2 (CHAINS C AND D) WHEN APPLIED TO MONOMER 1 (CHAINS A AND B). THE TRANSFORMATION PRESENTED AS *MTRIX 2* BELOW WILL YIELD APPROXIMATE COORDINATES FOR MONOMER 3 (CHAINS E AND F) WHEN APPLIED TO MONOMER 1 (CHAINS A AND B). THE TRANSFORMATIONS ARE DERIVED FROM THE POSITION OF THE NON-CRYSTALLOGRAPHIC THREE-FOLD SYMMETRY AXIS USED IN THE EARLY STAGES OF REFINEMENT WHEN STRICT THREE-FOLD SYMMETRY WAS IMPOSED ON THE STRUCTURE. THIS AXIS IS ALSO USED IN AVERAGING ELECTRON DENSITY MAPS.

INFLUENZA VIRUS HEMAGGLUTININ, Viral protein

MKTIIALSYIFCLALGQDLPGNDNSTATLCLGHHAVPNGTLVKTITDDQIEVTNATELVQSSSTGKICNNPHRILDGIDC
TLIDALLGDPHCDVFQNETWDLFVERSKAFSNCYPYDVPDYASLRSLVASSGTLEFITEGFTWTGVTQNGGSNACKRGPG
SGFFSRLNWLTKSGSTYPVLNVTMPNNDNFDKLYIWGIHHPSTNQEQTSLYVQASGRVTVSTRRSQQTIIPNIGSRPWVR
GLSSRISIYWTIVKPGDVLVINSNGNLIAPRGYFKMRTGKSSIMRSDAPIDTCISECITPNGSIPNDKPFQNVNKITYGA
CPKYVKQNTLKLATGMRNVPEKQTRGLFGAIAGFIENGWEGMIDGWYGFRHQNSEGTGQAADLKSTQAAIDQINGKLNRV
IEKTNEKFHQIEKEFSEVEGRIQDLEKYVEDTKIDLWSYNAELLVALENQHTIDLTDSEMNKLFEKTRRQLRENAEEMGN
GCFKIYHKCDNACIESIRNGTYDHDVYRDEALNNRFQIKGVELKSGYKDWILWISFAISCFLLCVVLLGFIMWACQRGNI
RCNICI