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J L Strominger

Publications and source records attributed to J L Strominger.

At least 595 records · Page 33Linked to original sources
PubMed1972

Enzymic removal and re-expression of a histocompatibility antigen, HL-A 2, at the surface of human peripheral lymphocytes ( 31 Cr-labeled cells-papain-puromycin-actinomycin D).

The removal by papain of a histocompatibility antigen, HL-A 2, from the surface of intact peripheral blood lymphocytes has been examined. Up to 80% of the antigenic determinant can be removed within 90 minutes. If the cells are reincubated in nutritive medium, re-expression of HL-A 2 is complete within 6 hours. Re-expression is reversibly inhibited by puromycin (50 mug/ml), but actinomycin D (6 mug/ml) only partially inhibited re-expression after 2 hours of prior incubation with the drug.

Antigens↗
PubMed1972

Isolation by covalent affinity chromatography of the penicillin-binding components from membranes of Bacillus subtilis.

An affinity chromatography technique was developed to isolate the five penicillin-binding components present in Bacillus subtilis membranes. The proteins were solubilized by the detergent Nonidet P-40, bound covalently to penicillin-substituted Sepharose, and subsequently eluted from the matrix with neutral hydroxylamine, which cleaves the penicilloyl-enzyme bond. Penicillin binding-component V, the D-alanine carboxypeptidase, makes up 1% of the total membrane protein. A modification of the above procedure enabled this enzyme to be obtained from the membrane in pure form in a single step with 50% overall recovery of enzymatic activity.

Alanine↗
PubMed1972

Inhibition of sterol biosynthesis by bacitracin.

Bacitracin is an inhibitor of the biosynthesis of squalene and sterols from mevalonic acid, C(5)-isopentenyl pyrophosphate, or C(15)-farnesyl pyrophosphate catalyzed by preparations from rat liver. The antibiotic is active at extremely low ratios of antibiotic to substrate. The mechanism of inhibition appears to be the formation of a complex between bacitracin, divalent cation, and C(15)-farnesyl pyrophosphate and other isoprenyl pyrophosphates. It is similar to the formation of the complex with C(55)-isopropenyl pyrophosphate in microbial systems. The toxicity of bacitracin for animal cells could be due in part to the formation of these complexes.

Alkaline Phosphatase↗
PubMed1972

Introducting of the 3-deoxy group in 3,6-dideoxyhexoses: a novel cofactor function for pyridoxamine-5'-phosphate.

A cofactor needed for the reduction of CDP-4-keto-6-deoxy-D-glucose to CDP-4-keto-3,6-dideoxy D-glucose has been detected and purified. Its spectra in neutral, acid, and basic solutions, its behavior on thin-layer chromatography, and other properties led to its identification as pyridoxamine-5'-phosphate. Moreover, authentic pyridoxamine-5'-phosphate substituted for the purified cofactor with about the same specific activity. Other vitamin B(6) derivatives did not stimulate the reaction, and inhibition was observed with some of them.

Chromatography, Ion Exchange↗
PubMed1972

Complex lipid requirements for detergent-solubilized phosphoacetylmuramyl-pentapeptide translocase from Micrococcus luteus.

Phospho-MurNAc-pentapeptide translocase activity in the membrane of M. luteus was lost upon addition of the detergent, Triton X-100, but could be restored by addition of lipid fractions to the assay. By assay in the presence of lipid, the activity of the Triton-solubilized enzyme could be measured. The synthesis of C(55)-isoprenyl-P-P-MurNAc-pentapeptide from UDP-MurNAc-pentapeptide required C(55)-isoprenyl-P, and was stimulated by a neutral lipid. The exchange reaction of UDP-MurNAc-pentapeptide with UMP required a polar lipid fraction, but the reaction was not affected by C(55)-isoprenyl-P or the neutral lipid. Thus, measurement of activity of the detergent-solubilized enzyme requires addition of three lipids, the lipid substrate (C(55)-isoprenyl-P), the neutral lipid, and a polar lipid.

Carbon Isotopes↗
PubMed1972

Isolation of polyisoprenyl alcohols from Streptococcus faecalis.

C(55)-isoprenyl alcohol and its derivatives have been isolated from Streptococcus faecalis and characterized. The relative amounts present as free alcohol, neutral lipid esters, and phosphate ester derivatives were determined. The chain lengths, mass spectra, and cis to trans ratio of double bonds are reported.

Alcohols↗
PubMed1971

C 55 -isoprenoid alcohol phosphokinase: an extremely hydrophobic protein from the bacterial membrane.

C(55)-isoprenoid alcohol phosphokinase, a butanol-soluble enzyme from the membrane of Staphylococcus aureus, has been purified to homogeneity by the inclusion of organic solvents in all of the techniques used. By polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, the enzyme is a single polypeptide chain of molecular weight 17,000. The amino-acid analysis reveals an unusually high content of nonpolar amino acids (58%), the largest amount so far reported in any protein. When equilibrated in butanol-water, enzyme apoprotein is found in the butanol layer. The influence of sodium chloride indicates that the lipid requirement of the enzyme is nonelectrostatic in nature.

Alcohols↗
PubMed1971

Inactivation of D-alanine carboxypeptidase by penicillins and cephalosporins is not lethal in Bacillus subtilis.

The D-alanine carboxypeptidase of Bacillus subtilis is a particulate enzyme that is irreversibly inactivated by penicillins and cephalosporins. However, the lethal concentrations of these antibiotics are not the same as those that inhibit enzymatic activity in vitro. 6-Aminopenicillanic acid inactivates at least 95% of the enzyme at nonlethal concentrations. Conversely, cephalothin is lethal at concentrations that do not inactivate the enzyme. Experiments with intact, growing cells confirm the results obtained in vitro. Therefore, a killing site distinct from the carboxypeptidase must be postulated.

Alanine↗
PubMed1971

Mechanism of action of bacitracin: complexation with metal ion and C 55 -isoprenyl pyrophosphate.

The inhibition by bacitracin of the enzymatic dephosphorylation of C(55)-isoprenyl pyrophosphate is abolished by the addition of chelating agents. If, however, the chelating agent is added after a preincubation of bacitracin with a divalent cation and the lipid substrate, then its addition has little effect, indicating that bacitracin, metal ion, and C(55)-isoprenyl pyrophosphate form a complex. Various divalent cations can participate in complex formation, but monovalent cations are ineffective. A direct demonstration of the formation of a complex between the C(55)-isoprenyl pyrophosphate and bacitracin in the presence of metal ions was obtained. Molecular models that show one possible conformation for a complex between bacitracin and the C(55)-isoprenyl pyrophosphate, in which the metal ion acts as a bridge between the two compounds, are presented.

Bacitracin↗