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Biomedical subjects

J M Brewer

Publications and source records attributed to J M Brewer.

At least 91 records · Page 5Linked to original sources
PubMed1976

Stopped-flow studies of changes in fluorescence of 8-anilino-1-naphthalene sulfonic acid caused by magnesium and salt binding to yeast enolase.

Stopped-flow studies of magnesium and salt (potassium chloride and acetate) effects on yeast enolase were carried out by following 8-anilino-1-naphthalenesulfonic acid fluorescence changes. The fluorescence changes appear to be largely caused by subunit association and dissociation, though there is evidence in some reactions for large changes in fluorescence occurring within the dead time of the stopped-flow measurements. These data are combined with measurements of initial enzyme activity after incubation in various solvents with or without magnesium to obtain subunit association and dissociation rates. From these, it is concluded that magnesium and the salts act by directly changing the affinities of the subunits for each other, apparently by producing a rapid change in protein conformation.

Acetates↗
PubMed1976

Chemical, physical and enzymatic comparisons of formyltetrahydrofolate synthetases from thermo- and mesophilic Clostridia.

Formyltetrahydrofolate synthetase from the mesophiles Clostridium cylindrosporum, C. acidiurici, and C. formicoaceticum and the thermophile C. thermoaceticum have been purified to homogeneity, the first two by Rabinowitz and Himes and their coworkers and the latter two by ourselves. The physical properties of these proteins are very similar. All four enzymes are tetrameric and all are activated by NH4+ or K+, and the mechanism of this activation always involves a decrease in Km for formate. The enzyme from C. formicoaceticum is more thermostable and has a higher temperature optimum than the C. cylindrosporum or C. acidiurici enzymes and the C. thermoaceticum enzyme is the most thermostable. Comparisons of the amino acid compositions indicate possible correlations between thermostability and an increased content of isoleucine, arginine and tryptophan and a decreased content of phenylalanine and aspartic acid. Both of the less thermostable enzymes dissociative above 37 degrees if NH4+ or K+ are removed, but neither of the more stable enzymes do. In 25% D2O, the C. formicoaceticum enzyme is destabilized at elevated temperatures, relative to the C. thermoaceticum enzyme. It is possible that stronger hydrophobic interactions between subunits are responsible for increased thermostability in these enzymes.

Amino Acids↗
PubMed1974

The molecular weight of J chains derived from human immunoglobulin M.

J chain was isolated from sulphonated human immunoglobulin M molecules by electrophoresis on polyacrylamide gels. When determined by electrophoresis in sodium dodecyl sulphate-polyacrylamide gels, the molecular weight of the protein was about 27000. After suspension in 5m-guanidine hydrochloride solution for 21 days, two groups of three bands appeared on the gels. Most of the protein dissociated to components of molecular weight 15000. The molecular weight of purified J chain was also determined by ultracentrifugation. In borate-saline solution the average weight-average molecular weight was about 29000. The molecular weight slowly decreased upon prolonged exposure to guanidine hydrochloride, and after 14 days the minimum molecular weight was about 15000. Some association between chains still existed. These data suggest that J chain derived from the paraprotein exists in borate-saline solution as dimers held by strong non-covalent forces.

Chromatography, Gel↗