Search PubMed⌕ Search

Biomedical subjects

C Lazdunski

Publications and source records attributed to C Lazdunski.

At least 109 records · Page 6Linked to original sources
PubMed1982

Colicins: a minireview.

Colicin are toxins that kill specifically E. coli bacteria. These cells have both an outer and a cytoplasmic membrane. Thus, three steps can be distinguished in colicin action: a) the interaction with specific receptors located at the cell surface, b) the uptake through the outer and eventually through the inner membrane, c) the action of the cell target that leads to cell death. In this short review, an overlook of these three steps is given.

Colicins↗
PubMed1982

Physical map of pColA-CA31, an amplifiable plasmid, and location of colicin A structural gene.

Evidence showing that the plasmic ColA, derived from strain CA31[pColA] can be amplified in the presence of chloramphenicol is presented. This plasmid has been purified and its Mr-value has been found to be 4.6 X 10(6) or 7 kb. Twelve cleavage sites have been mapped in pColA by using single and double restriction endonuclease digestions. These sites were ordered in relation to the single HindIII site. The other restriction endonucleases used were, respectively, SmaI, AvaI, PstI and HincII. Establishment of the map was helped by hybridization of pColA endonuclease digest products with 32P-labeled colicin A-mRNA. The structural gene for colicin A was contained in a 2.17-kb HincII fragment.

Chloramphenicol↗
PubMed1982

The receptor of bacteriophage lambda: evidence for a biosynthesis dependent on lipid synthesis.

Inhibition of lipid synthesis in cerulenin-treated cells or in a mutant strain defective in sn-glycerol-3-phosphate acyltransferase after glycerol deprivation, results in a marked decrease of insertion of lamB protein into the outer membrane. No lambda receptor was found in any other cell compartment or in the medium under these conditions. The LamB protein synthesis was inhibited by about 70% in the absence of lipid synthesis. The residual 30% protein produced during inhibition of fatty-acid or phospholipid synthesis, was probably incorporated into the outer membrane since no further incorporation was observed after resumption of these syntheses. Besides OmpF and OmpC protein [Bocquet-Pagès, C., Lazdunski, C., and Lazdunski, A. (1981) Eur. J. Biochem. 118, 105-111], at least four other proteins of the outer membrane are also subject to alteration of levels in the absence of lipid synthesis. Under these conditions the uptake of maltose, like the uptake of 5'AMP [Bocquet-Pagès, C., Lazdunski, C., and Lazdunski, A. (1981) Eur. J. Biochem. 118, 105-111], was inhibited as much as 60%. These results are discussed with regard to the biosynthesis and assembly of the outer membrane proteins.

Bacterial Outer Membrane Proteins↗
PubMed1982

Biosynthesis of Escherichia coli Braun's lipoprotein precursors in vitro and binding to membrane vesicles.

A cell-free system only programmed by endogenous mRNA present in a 30000 X g supernatant fraction is described in which 15-40% of the material produced was constituted by two lipoprotein precursors. These two polypeptides (a) are immunologically related, (b) contain the signal peptide and (c) apparently differ by the presence in one of them of a substituent on the -SH group of the single cysteine residue. The nature of this substituent could not be determined but no evidence was obtained that it could be a glyceride. No processing of any of these prolipoprotein forms could be demonstrated by addition of either Triton X-100 or membrane vesicles. A similar binding of both precursors to inverted membrane vesicles was observed when they were provided either co-translationally or post-translationally and this reaction occurred without the help of major membrane compounds.

Amino Acid Sequence↗
PubMed1982

Maturation of exported proteins in Escherichia coli. Requirement for energy, site and kinetics of processing.

Precursor forms of periplasmic and outer membrane proteins were accumulated in phenethyl-alcohol-treated cells in membrane fractions. After removal of phenethyl alcohol, maturation occurred in the absence but not in the presence of carbonylcyanide m-chlorophenylhydrazone (30 microM). The site and kinetics of processing were investigated for OmpA, LamB and OmpF proteins and for maltose binding protein and TEM beta-lactamase. With regard to sites of processing, no fundamental difference between outer membrane and periplasmic proteins was observed. For maltose binding protein and TEM beta-lactamase, maturation, like that of outer membrane protein precursors, occurred in membrane fractions. Processing of pro-OmpA protein was about as fast as that of pro-LamB protein whereas pro-OmpF protein appeared to mature more slowly. While carbonylcyanide m-chlorophenylhydrazone (30 microM) prevented processing of all precursor forms, arsenate, which alters formation of ATP even when it was used at 1 mM, did not totally prevent maturation occurring. These results are discussed with regard to the biosynthesis and assembly of exported proteins.

Bacterial Proteins↗
PubMed1981

Biosynthesis and export of colicin A in Citrobacter freundii CA31.

Synthesis of colicin A after induction with mitomycin C was studied. Specific inhibition of chromosomal protein synthesis occurred very shortly after mitomycin addition. There was no coordinate synthesis of colicin A (61000 Mr) and low-molecular-weight protein. Free and membrane-bound polysome fractions were isolated from cells induced with mitomycin C. Colicin A is synthesized in vitro in the free polysomes and not in the membrane-bound polysomes. Conditions are described which allow a practically specific labelling of colicin A in vivo. By using this system it was possible to demonstrate that colicin A is not transferred cotranslationally across the cytoplasmic membrane. In contrast, this protein leaves the cell where it was made long after synthesis. Preliminary evidence, suggesting that pauses occur during synthesis of colicin A, is presented.

Citrobacter↗
PubMed1981

[Biosynthesis of colicin A : existence of pauses in the translation of messenger RNA].

Evidence has been obtained for the existence of nascent polypeptide chains, that transiently accumulate as discrete size classes, due to discontinuities in the translation process of the colicin A mRNA. Existence of these discontinuities is independent of the hot cell of colicinogenic factor, and from the induction of synthesis by mitomycin C. The information that leads to the existence of discontinuities in the mRNA translation is contained in the plasmid Col A and, very likely, in the Col A gene itself.

Colicins↗
PubMed1981

Secretion into the bacterial periplasmic space of chicken ovalbumin synthesized in Escherichia coli.

Ovalbumin is secreted by the tubular gland cells without cleavage of a signal sequence at the N-terminus. In Escherichia coli strains which produce a chicken ovalbumin-like protein (OLP) from a plasmid-cloned gene, the OLP is synthesized on membrane-bound polysomes and secreted without cleavage into the periplasmic space. In contrast, a deleted protein, which lacks 126 amino acids in the N-terminal half, is not secreted and is synthesized from free polysomes. Our results are compatible with the presence, in the N-terminal half of the molecule, of a signal sequence necessary for the transport across the membrane.

Animals↗
PubMed1981

Lipid-synthesis-dependent biosynthesis (or assembly) of major outer-membrane proteins of Escherichia coli.

Upon inhibition of fatty acid synthesis in the presence of cerulenin, the uptake of 5' AMP and of other nutrients using similar pore systems can be inhibited as much as 70%. The same effect was observed upon inhibition of phospholipid synthesis after glycerol deprivation in a mutant strain defective in sn-glycerol-3-phosphate acyltransferase. Resumption of both fatty acid synthesis and phospholipid synthesis restores a normal uptake of 5' AMP. The protein composition of the outer membranes, analyzed after pulse radiolabelling by [35S]methionine, was mainly altered in OmpF and OmpC proteins. These proteins are the main porins used by most nutrients like 5' AMP. Whereas the synthesis or the assembly of OmpF protein seems to be more inhibited that that of OmpC protein after inhibition of fatty acid synthesis, the reverse case was observed after inhibition of phospholipid synthesis. No protein produced during inhibition of fatty-acid or phospholipid synthesis is reincorporated into the outer membrane after resumption of these syntheses. These results are discussed with regard to the biosynthesis and assembly of these proteins.

Adenosine Monophosphate↗
PubMed1981

Exclusive localization of colicin A in cell cytoplasm of producing bacteria.

The production of colicin A in Citrobacter freundii and in Escherichia coli was studied. After induction with low concentrations of mitomycin C, these organisms differed with regards to cell growth, cell viability, and kinetics of colicin A biosynthesis. Despite these differences, immunoferritin labelling on ultra-thin sections of induced frozen cells demonstrated that colicin A was located exclusively within the cell cytoplasm in both types of bacteria. By using protein markers, it was shown that at no time after induction was colicin A accumulated in the periplasmic space or in inner or outer membranes. These results were confirmed by a biochemical approach. For at least 3 h after induction, colicin A remained associated with producing cells and no colicin A activity was found in the periplasmic space. These results are discussed with reference to the synthesis and export of other bacteriocins.

Citrobacter↗
PubMed1979

Procaine, a local anesthetic interacting with the cell membrane, inhibits the processing of precursor forms of periplasmic proteins in Escherichia coli.

Treatment of Escherichia coli cells with procaine (0.55%, w/v) results in the accumulation of precursor in addition to mature forms of two periplasmic proteins, alkaline phosphatase and glutamine-binding protein. The precursor form of alkaline phosphatase has a higher molecular weight than the mature form by about 2600. An experimental technique is described to isolate and purify precursor forms of any presumably exported protein. After the membrane solubilization step in the presence of nonionic detergent, a peptidase is stimulated, resulting in partial cleavage of the precursors. The products of this cleavage have been identified as the mature protein and presumably the signal peptide in the case of alkaline phosphatase. The amino acid composition of this peptide, which is comprised of 25 residues, has been determined. Procaine (0.55%, w/v) causes an increase in molecular packing of lipid molecules in the membrane which might result in an alteration of membrane fluidity sufficient for selective inhibition of processing of precursors of exported proteins.

Alkaline Phosphatase↗
PubMed1978

[Procaine, a local anesthetic, interacting with the cell membrane and inhibiting the processing of exported protein precursors in Escherichia coli].

In E. coli cells grown in the presence of procaine (0.55% w/v), precursor forms of alkaline phosphatase and of glutamine binding protein accumulate besides mature forms synthesized prior to procaine addition. An experimental technique, of general application, for isolation and purification of mature and precursor forms obtained under these conditions, is described.

Alkaline Phosphatase↗