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Biomedical subjects

I A Wilson

Publications and source records attributed to I A Wilson.

At least 145 records · Page 8Linked to original sources
PubMed1985

Identical short peptide sequences in unrelated proteins can have different conformations: a testing ground for theories of immune recognition.

The ability of antibodies raised against disordered short peptides to interact frequently with their cognate sequences in intact folded proteins has raised a major theoretical issue in protein chemistry. We propose to address this issue by using antibodies raised against peptides with identical sequences, but different conformations, in pairs of unrelated proteins of known three-dimensional structure. The general search method presented here enabled us to detect candidate sequences for such immunological studies.

Animals↗
PubMed1984

The structure of an antigenic determinant in a protein.

The immunogenic and antigenic determinants of a synthetic peptide and the corresponding antigenic determinants in the parent protein have been elucidated. Four determinants have been defined by reactivity of a large panel of antipeptide monoclonal antibodies with short, overlapping peptides (7-28 amino acids), the immunizing peptide (36 amino acids), and the intact parent protein (the influenza virus hemagglutinin, HA). The majority of the antipeptide antibodies that also react strongly with the intact protein recognize one specific nine amino acid sequence. This immunodominant peptide determinant is located in the subunit interface in the HA trimeric structure. The relative inaccessibility of this site implies that antibody binding to the protein is to a more unfolded HA conformation. This antigenic determinant differs from those previously described for the hemagglutinin and clearly demonstrates the ability of synthetic peptides to generate antibodies that interact with regions of the protein not immunogenic or generally accessible when the protein is the immunogen.

Amino Acid Sequence↗
PubMed1984

A carbohydrate side chain on hemagglutinins of Hong Kong influenza viruses inhibits recognition by a monoclonal antibody.

A single amino acid substitution, Asp-63 to Asn-63, was detected in the hemagglutinin of an antigenic variant of the 1968 Hong Kong (H3) influenza virus that was selected by growth of the wild-type virus in the presence of a monoclonal antibody. The mutation generates an oligosaccharide attachment site, Asn-Cys-Thr at residues 63-65, that is glycosylated. Immunoprecipitation experiments with extracts from variant virus-infected cells prepared in the presence or absence of tunicamycin, which inhibits glycosylation, demonstrate that addition of the new oligosaccharide side chain is required to prevent reaction with the monoclonal antibody. Similar experiments with the virus of the 1969 Hong Kong influenza epidemic, A/England/878/69, which also contains a hemagglutinin glycosylated at residue 63, support this conclusion and provide evidence for the epidemiological significance of carbohydrate-mediated modifications of hemagglutinin antigenicity.

Amino Acid Sequence↗
PubMed1983

Sequential mutations in hemagglutinins of influenza B virus isolates: definition of antigenic domains.

Comparative analysis of the amino acid sequences of hemagglutinins (HAs) of influenza B/Lee/40, B/Md/59, and B/HK/73 viruses has allowed examination of the molecular basis of antigenic variation in type B viruses. As seen with influenza type A viruses, antigenic drift in influenza B viruses proceeds mostly through the accumulation of amino acid substitutions within the HA1 portion of the HA molecule. However, the rate of variation observed among the influenza B virus HAs appears to be significantly lower than the observed rate of variation among influenza A virus HAs. The overall rate of amino acid change in the HA1s of the influenza B viruses studied is 2% per 10 years, whereas the HA1s of H3 influenza A viruses vary by 9.2% per 10 years. The sequences of the influenza B HAs were also examined in relation to the three-dimensional model for the A/Aichi/2/68 HA. When the primary amino acid sequences are compared, it appears that most of the important structural features of the type A HAs--such as the sialic acid binding site, the disulfide linkages, and the stem structure of the trimer--are conserved in the influenza B virus HAs. Regions are also identified where extensive amino acid substitutions have occurred among the three antigenically distinct influenza B virus HAs. The locations of these areas in the B HA structure correspond to antigenic regions proposed for the A virus HAs. In addition, modulation of antigenic regions in B virus HAs may also occur through amino acid deletions and variation in glycosylation sites.

Amino Acid Sequence↗
PubMed1983

Generation of protein-reactive antibodies by short peptides is an event of high frequency: implications for the structural basis of immune recognition.

Recent studies have shown that chemically synthesized small peptides can induce antibodies that often react with intact proteins regardless of their position in the folded molecule. These findings are difficult to explain in view of the experimental and theoretical data which suggest that in the absence of forces provided by the folded protein, small peptides in aqueous solution do not readily adopt stable structures. In order to rationalize the two findings, there has been general acceptance of a stochastic model which suggests that the multiple conformers of a peptide in solution induce sets of antibodies with a small percentage reactive with conformations shared by the folded protein. This stochastic model has become less tenable as the success rate for the generation of protein-reactive anti-peptide antibodies has grown. To test the stochastic model, we have used monoclonal anti-peptide antibodies as a way of estimating the frequency with which small peptides induce antibodies that react with folded proteins. We have made monoclonal antibodies to six chemically synthesized peptides from three proteins. The frequency with which the peptides induce protein-reactive antibodies is at least 4 orders of magnitude greater than expected from previous experimental work and vastly different from what would be predicted by calculating the possible number of peptide conformers in solution. These findings make the stochastic model less likely and lead to consideration of other models. Aside from their practical significance for generation of highly specific reagents, these findings may have important implications for the protein folding problem.

Amino Acid Sequence↗
PubMed1982

Changes in the conformation of influenza virus hemagglutinin at the pH optimum of virus-mediated membrane fusion.

A conformational change in the hemagglutinin glycoprotein of influenza virus has been observed to occur to pH values corresponding to those optimal for the membrane fusion activity of the virus. CD, electron microscopic, and sedimentation analyses show that, in the pH range 5.2-4.9, bromelain-solubilized hemagglutinin (BHA) aggregates as protein-protein rosettes and acquires the ability to bind both lipid vesicles and nonionic detergent. Trypsin treatment of BHA in the pH 5.0-induced conformation indicates that aggregation is a property of the BHA2 component and that the conformation change also involves BHA1. The implications of these observations for the role of the glycoprotein in membrane fusion are discussed.

Bromelains↗
PubMed1982

Effects of some drugs and peptide hormones on the responsiveness of the rabbit isolated gall-bladder to cholecystokinin.

1. The efficacies of some standard preparations of CCK were compared and the effects of some drugs and peptide hormones on the responsiveness of the rabbit isolated gall-bladder to cholecystokinin were studied with an established automatic method of estimating cholecystokinin. 2. Atropine, propranolol, phentolamine mesylate and lignocaine were shown to have no effect on the responsiveness of the rabbit isolated gall-bladder. 3. Glucagon, somatostatin, pentagastrin, pancreatic polypeptide, motilin and the Karolinska preparation of secretin had no effect on the preparation alone and caused only slight changes when given with cholecystokinin. 4. The Boots preparation of secretin exhibited a small cholecystokinin effect when given alone, but considerably inhibited cholecystokinin-induced contractions. 5. The desulphated C-terminal octapeptide of cholecystokinin also exhibited inhibitory effects.

Animals↗
PubMed1981

On the three-dimensional structure and catalytic mechanism of triose phosphate isomerase.

Triose phosphate isomerase is a dimeric enzyme of molecular mass 56 000 which catalyses the interconversion of dihydroxyacetone phosphate (DHAP) and D-glyceraldehyde-3-phosphate. The crystal structure of the enzyme from chicken muscle has been determined at a resolution of 2.5 A, and an independent determination of the structure of the yeast enzyme has just been completed at 3 A resolution. The conformation of the polypeptide chain is essentially identical in the two structures, and consists of an inner cylinder of eight strands of parallel beta-pleated sheet, with mostly helical segments connecting each strand. The active site is a pocket containing glutamic acid 165, which is believed to act as a base in the reaction. Crystallographic studies of the binding of DHAP to both the chicken and the yeast enzymes reveal a common mode of binding and suggest a mechanisms for catalysis involving polarization of the substrate carbonyl group.

Animals↗
PubMed1981

Structure of the haemagglutinin membrane glycoprotein of influenza virus at 3 A resolution.

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.

Binding Sites↗