The interaction between influenza virus hemagglutinin and its cell-surface receptor, 5-N-acetylneuraminic acid (sialic acid), was probed by the synthesis of 12 sialic acid analogs, including derivatives at the 2-carboxylate, 5-acetamido, 4-, 7-, and 9-hydroxyl, and glycosidic positions. The equilibrium dissociation constants of these analogs were determined by nuclear magnetic resonance spectroscopy. Ligand modifications that reduced or abolished binding included the replacement of the 2-carboxylate with a carboxamide, the substitution of azido or N-benzyloxycarbonyl groups for the 5-acetamido group, and the replacement of the 9-hydroxyl with amino or O-acetyl moieties. Modifications having little effect on binding included the introduction of longer chains at the 4-hydroxyl position, the replacement of the acetamido methyl group with an ethyl group, and the removal of the 7-hydroxyl group. X-ray diffraction studies yielded 3 A resolution crystal structures of hemagglutinin in complex with four of the synthetic analogs [alpha-2-O-methyl-, 4-O-acetyl-alpha-2-O-methyl-, 9-amino-9-deoxy-alpha-2-O-methyl-, and alpha-2-O-(4'-benzylamidocarboxybutyl)-N-acetylneuraminic acid] and with the naturally occurring cell-surface saccharide (alpha 2-3)sialyllactose. The X-ray studies unambiguously establish the position and orientation of bound sialic acid, indicate the position of the lactose group of (alpha 2-3)sialyllactose, and suggest the location of an alpha-glycosidic chain (4'-benzylamidocarboxybutyl) that increases the binding affinity of sialic acid by a factor of about 3. Although the protein complexed with alpha-2-O-methylsialic acid contains the mutation Gly-135-->Arg near the ligand binding site, the mutation apparently does not affect the ligand's position. The X-ray studies allow us to interpret the binding affinities in terms of the crystallographic structure. The results suggest further experiments which could lead to the design of tight binding inhibitors of possible therapeutic value.

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

Structure, conformation, and dynamics of bioactive oligosaccharides: theoretical approaches and experimental validations

Analysis of saccharide binding to Artocarpus integrifolia lectin reveals specific recognition of T-antigen (beta-D-Gal(1----3)D-GalNAc).

The development of a theoretical databank of transferable pseudoatoms for fast prediction of the electron densities and related electronic properties of proteins is described. Chemically unique pseudoatoms identified on the basis of common connectivity and bonding are extracted from ab initio molecular densities of a large number of small molecules using a least-squares projection technique in Fourier transform space. The performance of the databank is evaluated by comparison of the electron densities and electrostatic properties of the amino acids GLN, SER, and LEU and their dimers with those obtained from molecular calculations on the same test compounds. It is found that deformation density bond peaks are reproduced to within 0.02−0.10 e/A3, whereas electrostatic potentials, bond critical point indices, atomic charges, and molecular moments show differences with results from calculations performed directly on the test molecules which are comparable with or smaller than the spread of the values between ...

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Ab Initio Quality Electrostatic Atomic and Molecular Properties Including Intermolecular Energies from a Transferable Theoretical Pseudoatom Databank

2.2 A resolution structure analysis of two refined N-acetylneuraminyl-lactose--wheat germ agglutinin isolectin complexes.

http://journals.iucr.org/b/issues/1981/03/00/a19950/a19950.pdf

J. Ohanessian

Papers

Structure de la N-acétyllactosamine (acétamido-2 désoxy-2 O-β-d-galactopyrannosyl-4a-d-glucopyrannose)