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Journal ArticleDOI

Structure of the influenza virus haemagglutinin complexed with its receptor, sialic acid

TL;DR: The three-dimensional structures of influenza virus haemagglutinins complexed with cell receptor analogues show sialic acids bound to a pocket of conserved amino acids surrounded by antibody-binding sites, suggesting that antibodies neutralize virus infectivity by preventing virus-to-cell binding.
Abstract: The three-dimensional structures of influenza virus haemagglutinins complexed with cell receptor analogues show sialic acids bound to a pocket of conserved amino acids surrounded by antibody-binding sites. Sialic acid fills the conserved pocket, demonstrating that it is the influenza virus receptor. The proximity of the antibody-binding sites suggests that antibodies neutralize virus infectivity by preventing virus-to-cell binding. The structures suggest approaches to the design of anti-viral drugs that could block attachment of viruses to cells.
Citations
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Journal ArticleDOI
TL;DR: Wild aquatic bird populations have long been considered the natural reservoir for influenza A viruses with virus transmission from these birds seeding other avian and mammalian hosts, but recent studies in bats have suggested other reservoir species may also exist.

4,155 citations

Journal ArticleDOI
TL;DR: Comparisons to the soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) protein complex of vesicle fusion suggests that these molecules are all in the fusion-activated conformation and that the juxtaposition of the membrane anchor and fusion peptide, a recurring feature, is involved in the fused mechanism.
Abstract: Hemagglutinin (HA) is the receptor-binding and membrane fusion glycoprotein of influenza virus and the target for infectivity-neutralizing antibodies. The structures of three conformations of the ectodomain of the 1968 Hong Kong influenza virus HA have been determined by X-ray crystallography: the single-chain precursor, HA0; the metastable neutral-pH conformation found on virus, and the fusion pH-induced conformation. These structures provide a framework for designing and interpreting the results of experiments on the activity of HA in receptor binding, the generation of emerging and reemerging epidemics, and membrane fusion during viral entry. Structures of HA in complex with sialic acid receptor analogs, together with binding experiments, provide details of these low-affinity interactions in terms of the sialic acid substituents recognized and the HA residues involved in recognition. Neutralizing antibody-binding sites surround the receptor-binding pocket on the membrane-distal surface of HA, and the structures of the complexes between neutralizing monoclonal Fabs and HA indicate possible neutralization mechanisms. Cleavage of the biosynthetic precursor HA0 at a prominent loop in its structure primes HA for subsequent activation of membrane fusion at endosomal pH (Figure 1). Priming involves insertion of the fusion peptide into a charged pocket in the precursor; activation requires its extrusion towards the fusion target membrane, as the N terminus of a newly formed trimeric coiled coil, and repositioning of the C-terminal membrane anchor near the fusion peptide at the same end of a rod-shaped molecule. Comparison of this new HA conformation, which has been formed for membrane fusion, with the structures determined for other virus fusion glycoproteins suggests that these molecules are all in the fusion-activated conformation and that the juxtaposition of the membrane anchor and fusion peptide, a recurring feature, is involved in the fusion mechanism. Extension of these comparisons to the soluble N-ethyl-maleimide-sensitive factor attachment protein receptor (SNARE) protein complex of vesicle fusion allows a similar conclusion.

2,629 citations

Journal ArticleDOI
12 Oct 1989-Nature
TL;DR: Isolated variable domains may offer an alternative to monoclonal antibodies and serve as the key to building high-affinity human antibodies and the name 'single domain antibodies (dAbs)' is suggested for these antigen binding demands.
Abstract: IN antibodies, a heavy and a light chain variable domain, VH and VL, respectively, pack together and the hypervariable loops on each domain contribute to binding antigen1–4. We find, however, that isolated VH domains with good antigen-binding affinities can also be prepared. Using the polymerase chain reaction5, diverse libraries of VH genes were cloned from the spleen genomic DNA of mice immunized with either lysozyme or keyhole-limpet haemocyanin. From these libraries, VH domains were expressed and secreted from Escherichia coli. Binding activities were detected against both antigens, and two VH domains were characterized with affinities for lysozyme in the 20 nM range. Isolated variable domains may offer an alternative to monoclonal antibodies and serve as the key to building high-affinity human antibodies. We suggest the name 'single domain antibodies (dAbs)' for these antigen binding demands.

1,899 citations

Journal ArticleDOI
TL;DR: In this paper, the authors discuss the public health implications of the Spanish influenza pandemic of 1918-1919, which caused ≈50 million deaths worldwide and remains an ominous warning to public health.
Abstract: The “Spanish” influenza pandemic of 1918–1919, which caused ≈50 million deaths worldwide, remains an ominous warning to public health. Many questions about its origins, its unusual epidemiologic features, and the basis of its pathogenicity remain unanswered. The public health implications of the pandemic therefore remain in doubt even as we now grapple with the feared emergence of a pandemic caused by H5N1 or other virus. However, new information about the 1918 virus is emerging, for example, sequencing of the entire genome from archival autopsy tissues. But, the viral genome alone is unlikely to provide answers to some critical questions. Understanding the 1918 pandemic and its implications for future pandemics requires careful experimentation and in-depth historical analysis.

1,657 citations

References
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Journal ArticleDOI
TL;DR: This chapter discusses the different aspects of thiobarbituric acid assay of sialic acid, which is suitable for measuring the release of bound sialoic acid by sialidase and hydrolysis of sIALic acid-containing material must be carried out for the measurement of total sialsic acids.

6,264 citations

Journal ArticleDOI
01 Jan 1977
TL;DR: This review is concerned with the packing of groups of atoms in proteins and with the area of solvent-protein interfaces.
Abstract: The protein folding problem remains today one of the most intriguing and funda­ mental questions in biochemistry. For peptide chains the covalent connectivity, the general nature of the interatomic forces, and, in many cases, the final average structures are known, yet the details of the folding process remain a mystery. Some of the experimental work and differing ideas on theory are described in recent reviews ( 1 -4). When the structure of double-stranded DNA was first proposed there was wide­ spread excitement, not only because of the feeling of triumph accompanying a problem solved but also because of the apparent simplicity of the structure, one whose principal features could be characterized by a relatively small number of parameters. Great excitement also attended the first solution of the structure of a protein, myoglobin. However, this was accompanied not by rejoicing over simplicity but by wonder at the remarkable complexity of the answer. The structure did not immediately yield to simplifying descriptions. In the ensuing years a great deal of time and effort has been spent in trying to find useful descriptions. Homopolymers, or heteropolymers composed of short repeating sequences, tend to form extended structures, i.e. polyamino acids, collagen, silk, etc. The globular proteins are invariably formed from heteropolymers with nonrepeating sequences. Either type of polymer may form a-helical or fj structures, but the folding of such units into a compact particle is always associated with chains of non repeating sequence. Although globular protein structures can be described in terms of helices, extended chains, turns, and nonregular regions, this useful conformational descrip­ tion by itself has not yet led to an understanding of the structures. Some additional and different points of view are needed. This review is concerned with the packing of groups of atoms in proteins and with the area of solvent-protein interfaces. As far as possible the emphasis is on simple

2,447 citations

Journal ArticleDOI
29 Jan 1981-Nature
TL;DR: The haemagglutinin glycoprotein of influenza virus is a trimer comprising two structurally distinct regions: a triple-stranded coiled-coil of α-helices extends 76 Å from the membrane and a globular region of antiparallel β-sheet is positioned on top of this stem.
Abstract: The haemagglutinin glycoprotein of influenza virus is a trimer comprising two structurally distinct regions: a triple-stranded coiled-coil of alpha-helices extends 76 A from the membrane and a globular region of antiparallel beta-sheet, which contains the receptor binding site and the variable antigenic determinants, is positioned on top of this stem. Each subunit has an unusual loop-like topology, starting at the membrane, extending 135 A distally and folding back to enter the membrane.

2,444 citations

Journal ArticleDOI
05 Jul 1985-Science
TL;DR: Analysis of neighboring aromatic groups in four biphenyl peptides or peptide analogs and 34 proteins reveals a specific aromatic-aromatic interaction that helps stabilize tertiary structure, and 20 percent stabilize quaternary structure.
Abstract: Analysis of neighboring aromatic groups in four biphenyl peptides or peptide analogs and 34 proteins reveals a specific aromatic-aromatic interaction. Aromatic pairs (less than 7 A between phenyl ring centroids) were analyzed for the frequency of pair type, their interaction geometry (separation and dihedral angle), their nonbonded interaction energy, the secondary structural locations of interacting residues, their environment, and their conservation in related molecules. The results indicate that on average about 60 percent of aromatic side chains in proteins are involved in aromatic pairs, 80 percent of which form networks of three or more interacting aromatic side chains. Phenyl ring centroids are separated by a preferential distance of between 4.5 and 7 A, and dihedral angles approaching 90 degrees are most common. Nonbonded potential energy calculations indicate that a typical aromatic-aromatic interaction has energy of between -1 and -2 kilocalories per mole. The free energy contribution of the interaction depends on the environment of the aromatic pair. Buried or partially buried pairs constitute 80 percent of the surveyed sample and contribute a free energy of between -0.6 and -1.3 kilocalories per mole to the stability of the protein's structure at physiologic temperature. Of the proteins surveyed, 80 percent of these energetically favorable interactions stabilize tertiary structure, and 20 percent stabilize quaternary structure. Conservation of the interaction in related molecules is particularly striking.

2,300 citations

Journal ArticleDOI
29 Jan 1981-Nature
TL;DR: Four ‘antigenic sites’ on the three-dimensional structure of the influenza haemagglutinin are identified and at least one amino acid substitution in each site seems to be required for the production of new epidemic strains between 1968 and 1975.
Abstract: Four 'antigenic sites' on the three-dimensional structure of the influenza haemagglutinin are identified. At least one amino acid substitution in each site seems to be required for the production of new epidemic strains between 1968 and 1975.

1,530 citations