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Biomedical subjects

L B Tabatabai

Publications and source records attributed to L B Tabatabai.

4 recordsLinked to original sources
PubMed1979

Isolation and characterization of toxic fractions from Brucella abortus.

Two types of toxic fractions, protein-rich and carbohydrate-rich, were isolated from attenuated (strain 19) and virulent (strain 2308) Brucella abortus organisms. Polyacrylamide gel electrophoresis of the protein-rich fraction, in the presence and absence of sodium dodecyl sulfate, revealed qualitative and quantitative differences in the protein bands derived from the attenuated and virulent strains. Sodium dodecyl sulfate-gel electrophoresis indicated that the major differences between these protein fractions were in the molecular weight range from 14,000 to 40,000. Immunoelectrophoresis of these fractions from the attenuated and virulent strains revealed differences in the antigenic spectrum. Polypeptides in the carbohydrate-rich fraction could be visualized on polyacrylamide gels only when reacted with fluorescamine before electrophoresis. Immune sera did not precipitate the components of the carbohydrate-rich fraction. Intradermal injecttion of the protein and carbohydrate-rich fractions resulted in different types of skin lesions in guinea pigs, i.e., edematous/erythematous and necrotic lesions, respectively. Fractions derived from attenuated and virulent strains of B. abortus were equally toxic in the guinea pig skin test. The toxic activity of both types of fractions was susceptible to pronase and heat treatment.

Animals↗
PubMed1977

Studies on the specificity of phosphorylase kinase using peptide substrates.

The action of phosphorylase kinase on synthetic peptides is reported. These peptides are variants of the amino acid sequence. Ser-Asp-Gln-Glu-Lys-Arg-Lys-Gln-Ile-Ser-Val-Arg-Gly-Leu, found in the natural substrate, phosphorylase b. The effects of size, the cluster of basic groups at the NH2-terminal side, the phosphorylatable seryl residue, the hydrophobic groups surrounding serine, and the arginyl function at the COOH-terminal side were tested and analyzed by evaluation of the kinetic parameters, Km and Vmax. The first 6 residues were found to be nonessential, but substitution of residues in the sequence. Lys-Gln-Ile-Ser-Val-Arg, had a large effect on phosphorylation. A comparison was made between the action of nonactivated and activated phosphorylase kinase on selected peptides and phosphorylase b. Various forms of phosphorylase b were tested as substrates for cyclic AMP-dependent protein kinase in the presence of effectors and salts. Although phosphorylase would not serve as a substrate for protein kinase, the aforementioned synthetic peptide of the phosphorylase b sequence would do so, indicating that the primary sequence surrounding the phosphorylatable serine did not block phosphorylation, which suggests that higher order structural features prohibit the phosphorylation.

Amino Acids↗