PubMed Health⌕ Search

Biomedical subjects

J L Strominger

Publications and source records attributed to J L Strominger.

At least 559 records · Page 31Linked to original sources
PubMed1974

Penicillin-resistant temperature-sensitive mutants of Escherichia coli which synthesize hypo- or hyper-cross-linked peptidoglycan.

A group of Escherichia coli mutants which are ampicillin resistant at 32 C and which either are unable to grow or lyse at 42 C has been selected. These mutants have been classified by a number of characteristics: total peptidoglycan synthesis measured by [(14)C]diaminopimelic acid incorporation, extent of cross-linking of the peptidoglycan which is synthesized, growth characteristics at the two temperatures, and morphology. Two especially interesting groups of mutants have been described. In one of these, a hypo-cross-linked peptidoglycan was synthesized at the nonpermissive temperature. Most of these organisms lysed at 42 C. In another group, the peptidoglycan synthesized at 42 C was hyper-cross-linked. Many of these organisms were spherical. Studies of revertants indicated that ampicillin resistance, temperature sensitivity, cross-linking, growth characteristics, and morphological changes may be related to a single mutational event in both of these groups.

Ampicillin↗
PubMed1974

Mechanism of action and development of resistance to a new amidino penicillin.

The mechanism of killing of Escherichia coli by a novel beta-lactam antibiotic, an amidino penicillin, has been investigated. This compound converts E. coli to relatively stable spherical forms at low concentration. However, the amidino penicillin caused no alteration in any of those parameters of peptidoglycan synthesis which can be studied. Above 10 mug of the antibiotic per ml the cells began to lyse, and a second mode of killing appeared. Mutants resistant to the amidino penicillin were isolated and several were studied in detail. Three mutant phenotypes were distinguished: (i) spherical shape and hypersensitive to lysis by either amidino penicillin or ampicillin; (ii) spherical shape and normally sensitive to lysis; (iii) rod shape, converted to viable spheres by amidino penicillin and normally sensitive to lysis.

Amidines↗
PubMed1974

Inhibition of the Bacillus subtilis membrane-bound D-alanine carboxypeptidase by 6-aminopenicillanic acid covalently coupled to sepharose.

An insoluble penicillin derivative, 6-aminopenicillanic acid covalently coupled to Sepharose, was used to investigate the location of the d-alanine carboxypeptidase in the Bacillus subtilis membrane. Only 50% of the enzymatic activity in protoplasts and 74% of that in purified membranes was sensitive, although the purified enzyme could be inhibited completely by the resin. These results suggest that a minimum of 50% of the d-alanine carboxypeptidase exists on the outer face of the bacterial membrane.

Alanine↗
PubMed1974

Protein and carbohydrate composition of the cell envelope of Halobacterium salinarium.

The isolated cell envelope of Halobacterium salinarium strain 1 contained 15 to 20 proteins that were resolved by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. All but one of these proteins had molecular weights of 130,000 or less and together accounted for 50 to 60% of the total envelope protein. The remaining 40 to 50% of the envelope protein was accounted for by a single protein with an apparent molecular weight of approximately 194,000 that stained for carbohydrate with periodate-Schiff reagent. The proteolytic enzymes trypsin and Pronase were used to show that the carbohydrate is covalently bound to the protein. Separation of amino sugar- and hexose-containing tryptic peptides by gel filtration indicated that all of the nonlipid carbohydrate of the cell envelope is covalently bound to protein. The results of partial purification by phenol extraction indicated that both the amino sugar and hexose are bound to the 194,000-molecular-weight protein. Exposure of isolated cell envelopes to low salt concentration resulted in solubilization of a majority of the envelope proteins. A relatively small number of proteins, including the high-molecular-weight, carbohydrate-containing protein, remained bound to the sedimentable cell membrane fraction.

Bacterial Proteins↗
PubMed1973

Relation of detergent HLB number to solubilization and stabilization of D-alanine carboxypeptidase from Bacillus subtilis membranes.

The ability of various nonionic detergents to solubilize D-alanine carboxypeptidase and other membrane-bound enzymes was correlated to a physical property of the detergent, the HLB number. Only a fairly narrow range of detergents were effective solubilizing agents. Purified carboxypeptidase required either a detergent or detergent plus a lipid fraction for stability. Only those detergents effective in solubilizing the enzyme were effective in stabilizing it.

Alanine↗
PubMed1973

Papain-solubilized HL-A antigens from cultured human lymphocytes contain two peptide fragments.

HL-A 2 and HL-A 7 antigens have been solubilized from cultured human lymphocytes by papain and purified on a small radioactive scale after formation of immune complexes, or on a large scale by column chromatographic methods. In both cases, it has been shown that the materials obtained consist of two noncovalently bound fragments. One fragment is a glycopeptide of molecular weight 30,000-31,000, the other is a peptide of molecular weight 11,000-12,000. In polyacrylamide gels containing 8 M urea, the large fragments of HL-A 2 and HL-A 7 exhibited different electrophoretic mobilities, while the small fragments were the same. The relationship of these materials to the native HL-A molecule is discussed.

Antigen-Antibody Complex↗
PubMed1973

Additional antibiotic inhibitors of peptidoglycan synthesis.

Diumycin, janiemycin, nisin, and subtilin inhibited peptidoglycan synthesis catalyzed by particulate enzyme systems from Bacillus stearothermophilus and Escherichia coli. All of these, except for nisin, also induced accumulation of the lipid intermediate in peptidoglycan synthesis. Concentrations required for 50% inhibition of peptidoglycan synthesis were less than 0.1 mug/ml for diumycin and in the range of 10 to 100 mug/ml for janiemycin, nisin, and subtilin in both organisms. The discrepancy between the extremely low concentration of diumycin required to inhibit the in vitro system from E. coli and the much higher concentration required to inhibit growth of the organism is noteworthy.

Anti-Bacterial Agents↗