Biomedical subjects

S A Benner

Publications and source records attributed to S A Benner.

99 records · Page 6Linked to original sources

PubMed1987

Anomeric specificity of L-fucose dehydrogenase: a stereochemical imperative in aldopyranose dehydrogenases?

A set of hypotheses is proposed that explains the anomeric specificity of aldopyranose dehydrogenases in terms of an evolutionarily selected function. The first hypothesis, based on stereoelectronic theory, argues that, in the "allowed" transition state for oxidation at the anomeric carbon, the two oxygens attached to the anomeric carbon each bear a lone pair of electrons antiperiplanar to the departing "hydride". The second hypothesis is that the dehydrogenase is functionally constrained to bind the anomer that has this arrangement of lone pairs in its lowest energy chair conformer. The anomeric specificity of L-fucose dehydrogenase is experimentally examined. The enzyme oxidizes preferentially the beta-anomer, consistent with the prediction made by these hypotheses. Available experimental data for other enzymes (D-glucose-6-phosphate dehydrogenase, D-glucose dehydrogenase, D-galactose dehydrogenase, D-abequose dehydrogenase, and D-arabinose dehydrogenase) are found to be also consistent with the proposed hypotheses.

Animals↗

PubMed1987

Expression of bovine pancreatic ribonuclease A in Escherichia coli.

A synthetic gene for bovine pancreatic ribonuclease A (RNase A) has been expressed in Escherichia coli as a fusion protein with beta-galactosidase linked by the tetrapeptide Ile-Glu-Gly-Arg. RNase A was cleaved from the fusion using factor Xa, and the resulting product purified and reconstituted. The isolated RNase A was chromatographically, catalytically, and immunologically identical with authentic RNase A. This work argues that the method suggested by Nagai and Thogersen [Nagai, K. & Thogersen, H. C. (1984) Nature (Lond.) 309, 810-812] for releasing fusion proteins is quite general, even when applied to particularly complicated expression problem. The procedure here makes RNase A available for the first time as a model for studying structure-function relationships in proteins using site-directed mutagenesis.

Animals↗

PubMed1987

Natural selection, protein engineering, and the last riboorganism: rational model building in biochemistry.

A detailed study of the chemical behavior of modern catalysts (here, exemplified by dehydrogenases dependent on NAD+) allows us to construct models that distinguish between selected and drifting behaviors in biological macromolecules. These models enable us to manipulate rationally the properties of enzymes, here to design an "acetaldehyde reductase" dependent on NAD+ that is faster than any given us by nature. When applied to the origin of protein catalysis, models that explain the structures of ribo-cofactors (e.g., NAD+) must postulate a metabolically complex breakthrough organism. This means that: (1) The view from the present day back to the truly primeval organism is obscured; it is futile to try to deduce the detailed structure of the first life by examining the behaviors of modern organisms. (2) Riboorganisms dominated life on earth for a long time before translation evolved; indeed, fossils of riboorganisms might already be known. (3) Using organic synthesis, we have expanded the number of bases available for making RNA and making accessible RNA molecules that are likely to be intrinsically better catalysts.

Animals↗

PubMed1984

Total synthesis and cloning of a gene coding for the ribonuclease S protein.

A gene for ribonuclease S protein, has been chemically synthesized and cloned. The gene is designed to have 25 specific restriction endonuclease sites spaced at short intervals, permitting its structure to be rapidly modified. This flexibility facilitates tests of hypotheses relating the primary structure of the enzyme to its physical and catalytic behavior.

Amino Acid Sequence↗

PubMed1982

The stereoselectivity of alcohol dehydrogenases: a stereochemical imperative?

The stereoselectivity of NAD+-dependent alcohol dehydrogenases (transfering either the pro-R or pro-S hydrogen of NADH) correlates with the thermodynamic stability of their substrates, and appears to reflect evolutionary pressure to adjust in the active site the conformation of NADH so as to match the cofactor's reducing power to the oxidizability of the substrate. A requirement that the free energies of protein-bound intermediates be matched suggests a new approach for understanding catalysis and evolution in enzymes.

Alcohol Oxidoreductases↗

PubMed1980

Preparation of an ecdysone immunogen for radioimmunoassay work.

A highly improved procedure for the preparation of ecdysone-protein conjugates for immunological work is reported. Bovine thyroglobulin is succinylated and the succinylated protein is coupled to beta-ecdysone with 1-ethyl-3-(-dimethylaminopropyl)-carbodiimide in the presence of the acylation catalyst 4-dimethylaminopyridine, The antiserum obtained using this immunogen provides a radioimmunoassay sensitive to 25 pmol of beta-ecdysone. The anti-ecdysone antibody cross-reacts with alpha-ecdysone but not with cholesterol or progesterone. This procedure reverses the standard strategy for synthesizing ester linkages in hapten-protein conjugates and should have widespread applicability for the preparation of other such conjugates for immunological work.

Animals↗

PubMedDate not supplied

Predicting the conformation of proteins from sequences. Progress and future progress.

Recent progress in structure prediction has allowed bona fide predictions, those made and published before an experimental structure is determined, to be remarkably accurate. The most successful methods rely on an analysis of patterns of conservation and variation within homologous protein sequences, extract tertiary structural information before secondary structure is predicted, and avoid 'three state per residue scores' as a tool for evaluating a prediction, focusing instead on efforts to understand why a prediction is successful when it is successful, and why it fails when it fails.

Amino Acid Sequence↗

PubMedDate not supplied

The last ribo-organism.

Explore the source record for details and available documents.

Biological Evolution↗

PubMedDate not supplied

The IAIMS--an essential infrastructure for increasing the competitiveness of health care practices.

The eighth annual workshop of the IAIMS Consortium was devoted to exploring how information technology might provide the tools to allow health care practices to compete in the new health care environment while maintaining independence. The options that were discussed included: optimizing care of the patient in the local setting; reducing practice overhead by improving efficiency and effectiveness; and finding innovative strategies for providing health care and new products.

Economic Competition↗