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C Lazdunski

Publications and source records attributed to C Lazdunski.

At least 127 records · Page 7Linked to original sources
PubMed1978

Evidence for synthesis of alkaline phosphatase on membrane-bound polysomes in Escherichia coli.

Polysomes containing nascent chains of alkaline phosphatase have been isolated from a membrane-bound polysome preparation. Indirect immunoprecipitation using conformation-specific antibodies has been employed. This technique provides a good enrichment of these polyribosomes since routinely no more than than 10--15% of non-specific immunoprecipitation was observed. The yield of the procedure is generally 40% but can be increased if higher non-specific immunoprecipitation is tolerated. Antibodies, previously described, directed against uncoiled or folded monomers of alkaline phosphatase can be used as primary antibody to recognize the nascent chains contained in membrane-bound polysomes which suggests that these chains are partially folded.

Alkaline Phosphatase↗
PubMed1976

Isolation and genetic mapping of Escherichia coli aminopeptidase mutants.

Many mutant strains devoid of aminopeptidase activity have been isolated in Escherichia coli. All of them produce cross-reacting material when tested against specific antiaminopeptidase antibody. The map position of the locus specifying this enzyme has been determined by three conjugations and two P1 mediated transduction experiments. By analogy with Salmonella typhimurium this locus has been called pepN (Miller, 1975). Mutations in pepN are jointly transduced with fabA and pyrD at high frequency. These data and conjugation results suggest a location between 20.5 and 22.5 minutes on E. coli genetic map.

Aminopeptidases↗
PubMed1976

Effects of antibodies to various molecular forms of a mutationally altered Escherichia coli alkaline phosphatase on its activation by zinc.

Immunogenic and antigenic properties of a Zn2+ -deficient alkaline phosphatase produced in a mutant (U-47) of Escherichia coli have been studied. The native U-47 enzyme, that exists in a monomerdimer equilibrium, was used as immunogen. From the antisera obtained, four antibody populations directed to the various molecular forms of U-47 enzyme have been purified by affinity chromatography using specific antigens coupled to glutaraldehyde-activated beads of indubiose. 70% of the total antibody obtained was directed both to the monomeric and the dimeric forms, 9% was directed to the dimer but showed a low affinity for the monomer; 10% and 11% were specifically directed respectively to the monomer and the dimer. Each antibody population purified had a specific effect on the catalytic activity of the Zn2+ -activated U-47 enzyme. The anti-monomer-dimer and the anti-dimer-monomer inhibit to the same extent whereas the specific anti-monomer does not alter the activity significantly and the specific anti-dimer causes a 30% activation. The catalytic activity of the alkaline phosphatase produced in wild-type strains was also reduced by these anti-U-47 enzyme antibodies. However, whereas the anti-monomer had again very little effect, the anti-dimer-monomer and the anti-monomer-dimer inhibited this enzyme to different extents. The specific antidimer also inhibited this wild-type alkaline phosphate. Antibodies of high affinity to the dimeric form of U-47 enzyme, i.e. specific anti-dimer or anti-dimer-monomer, caused a 30% activation when they were added prior to the reactivation process by Zn2+. Specific anti-monomer strongly inhibited this reactivation process. The Fab fragment of the anti-wild-type phosphatase antibody, under the same conditions, caused a 300% activation. The extents of interactions of the various molecular forms of U-47 enzyme and of the wild-type enzyme with the anti-monomer-dimer and with the anti-dimer have been determined. U-47 enzyme monomeric form has three determinants exposed and the dimeric form has five determinants exposed for interacting with the anti-monomer-dimer antibody, the free wild-type enzyme has only two determinants exposed to this antibody. These determinants might be close to the active site or in another critical location since this antibody can reduce the catalytic activity of the wild-type enzyme to half the original value. The anti-dimer antibodies can interact with three determinants exposed at the surface of the free Zn2+ -reactivated U-47 enzyme and the non-covalent binding of one mole of inorganic phosphate results in the exposure of one more antigenic determinant.

Alkaline Phosphatase↗
PubMed1976

Existence, localization and regulation of the biosynthesis of aminoendopeptidase in gram-negative bacteria.

An enzyme capable of hydrolyzing the substrate L-alanine p-nitroanilide has been found in 18 gram-negative Enterobacteriaceae and Pseudomonas that we tested. This enzyme might be located near the cell surface. Contrastingly we have not detected this activity on colonies of the 8 gram-positive Bacillus that we tested, which suggest a taxonomic value for this test. The aminoendopeptidases found in the various gram-negative bacteria showed similar electrophoretic mobilities and immunological cross-reactivity when tested again Escherichia coli anti-aminoendopeptidase antiserum. The regulation of aminoendopeptidase biosynthesis by the endogenous level of inorganic phosphate that we previously demonstrated in E. coli has been found to exist in all gram-negative organisms tested.

Alanine↗
PubMed1975

Evidence for an aminoendopeptidase localized near the cell surface of Escherichia coli. Regulation of synthesis by inorganic phosphate.

An enzyme capable of hydrolyzing the substrate L-alanine p-nitroanilide has been found in the various Escherichia coli strains tested. This enzyme has been called aminoendopeptidase since it shows both activities (see accompanying paper). It is released from the cells by osmotic shock and by lysozyme -- EDTA spheroplasting treatment, and 50% of the total activity is directly detectable with suspensions of intact cells. However, the release by osmotic shock or spheroplasting is not as efficient as it is for alkaline phosphatase. This periplasmic aminoendopeptidase is constitutively produced but the differential rate of synthesis is increased 4-fold when the cell growth is limited by Pi. The occurrence of this 'derepression' is simultaneous with that of alkaline phosphatase. Increasing the concentration of inorganic phosphate in the medium has no effect on the constitutive aminoendopeptidase synthesis. The effect of phosphate starvation is specific since starvation for neither nitrogen nor carbon and energy source are effective in derepressing aminoendopeptidase.

Alkaline Phosphatase↗
PubMed1975

Regulation of Escherichia coli K10 aminoendopeptidase synthesis. Effects of mutations involved in the regulation of alkaline phosphatase.

The synthesis of alkaline phosphatase in Escherichia coli is controlled by the action of at least four genes denoted phoS, phoT, phoR and phoB. The effect of mutations in the first three of these genes on the synthesis of periplasmic aminoendopeptidase of E. coli K 10 have been investigated. phoR gene product does not seem to be involved either in the constitutive or in the derepressed synthesis of this enzyme. Mutations in phoS or phoT influence the intracellular level of Pi in much the same way as depletion of Pi from the growth medium, and only as a consequence influence the synthesis of aminoendopeptidase and alkaline phosphatase. Point, amber or deletion mutations in the alkaline phosphatase structural gene do not affect aminoendopeptidase synthesis. Thus, alkaline phosphatase and 'derepressed' aminoendopeptidase synthesis are co-regulated by the endogenous level of inorganic phosphate. The way by which this regulation operates is discussed.

Alkaline Phosphatase↗
PubMed1975

Purification and properties of a periplasmic aminoendopeptidase from Escherichia coli.

A periplasmic aminoendopeptidase from Escherichia coli has been purified to hemogeneity. It is a monomer of molecular weight 45000 and containing one -- SH group that is necessary for catalytic activity. The study of its substrate specificity indicated that the enzyme has both aminopeptidase and endopeptidase activity. The pH optimum for L-alanine p-nitroanilide hydrolysis is between 7 and 7.5 and that for 125I-labeled casein proteolysis between 7.3 and 7.6. The activation energy for the hydrolysis of L-anine p-nitroanilide was calculated to be 5.3 kcal X mol-1 (22.2 kJ X mol-1).

Amino Acids↗
PubMed1975

Different cyclic adenosine 3',5'-monophosphate requirements for induction of beta-galactosidase and tryptophanase. Effect of osmotic pressure on intracellular cyclic adenosine 3,5-monophosphate concentrations.

In this study we have tried to answer the following questions: (1) is it possible for different catabolite-repressible genes, although submitted to the same control, to be expressed selectively depending upon the growth conditions, and (2) what is the effect of increasing the osmolarity of the medium on the intracellular level of cAMP? Two conditions were found to cause a continuous variation of intracellular cAMP levels during growth. With different strains, higher cAMP levels are required for induction of the tryptophanase gene than one required for induction of the lactose operon. cAMP has been provided externally in adenyl cyclase minus cells of a mutant that has been made permeable by EDTA treatment. Although external cAMP concentrations, 10 times higher than the usual intracellular levels, are required for induction of beta-galactosidase and tryptophanase, the difference of requirements of cAMP is maintained. An increase in the osmolarity of the medium by sucrose addition causes a fourfold decrease in the intracellular cAMP level. As a consequence this prevents the induction of tryptophanase whereas beta-galactosidase is still inducible. After pulse induction, a difference in the kinetics of expression of the tryptophanase and beta-galactosidase genes was found. Its relationship with the previous results is discussed.

Adenylyl Cyclases↗
PubMed1975

On the control of septation in Escherichia coli.

Mutants of E. coli defective in cell septation (ftsA to ftsG, conditional thermosensitive mutants isolated by Ricard and Hirota) were studied with respect to their membrane protein composition, murein hydrolase activities and rates of synthesis of murein and phospholipids. Three classes of mutants have been distinguished: 1) those affected in both murein and phospholipid synthesis; 2) those affected in either murein or phospholipid synthesis and 3) those affected in neither of these parameters. Overall murein hydrolase activities, after activation, is of the same order in all the mutants screened. In addition to soluble products of murein splitting, we have found insoluble products that appear to be in dynamic equilibrium with the murein of the sacculus. Endogenous levels of cyclic adenosine 3',5'-monophosphate measured after blocking septation showed no variation. This suggests that the cyclic nucleotide is not involved in the metabolic control of septation.

Bacterial Proteins↗