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W Goebel

Publications and source records attributed to W Goebel.

At least 127 records · Page 7Linked to original sources
PubMed1994

Ultrastructural study of Listeria monocytogenes entry into cultured human colonic epithelial cells.

Evidence that Listeria monocytogenes enters Caco-2 cells through the apical surface is presented. Attachment of bacteria to host cells seems to induce modifications of microvilli which are either in direct contact with the bacterial surface or in close vicinity, resulting in the formation of lamellipodia involved in the cellular uptake of the bacteria. Such modifications are not induced by L. monocytogenes SLCC 53, which carries a deletion in the prfA gene, although attachment of this mutant to Caco-2 cells occurs. Listeria innocua does not attach well to Caco-2 cells and also fails to cause structural alterations of the microvilli. Treatment of confluent monolayers of Caco-2 cells with ethylene glycol-bis(beta-aminoethyl ether)- N,N,N1,N1-tetraacetic acid (EGTA), which disrupts intercellular junctions, greatly reduced the uptake of Listeria cells. Attachment and invasion of L. monocytogenes was not accompanied by accumulation of filamentous actin around the entering bacterial cell.

Bacterial Adhesion↗
PubMed1994

Synthesis and secretion of bacterial antigens by attenuated Salmonella via the Escherichia coli hemolysin secretion system.

We describe a plasmid system which allows the secretion of foreign antigens in attenuated Salmonella aroA strains by the secretion apparatus of E. coli hemolysin. The gene (or gene fragment) encoding the antigen is inserted in frame into a residual position of the hlyA gene, encoding the HlyA secretion signal (HlyAs). Generally, the fused gene is efficiently expressed and the synthesized antigen is in part secreted into the culture supernatant and in part exposed on the surface of the producing Salmonella strain. The successful use of this approach is demonstrated with two antigens of Salmonella typhimurium, PagC and SlyA, both of which are potent virulence factors but produced only in small amounts under in vitro culture conditions and two virulence proteins of Listeria monocytogenes, p60 and listeriolysin. Interestingly the listeriolysin fusion protein proved to be cytolytically active and allowed, when expressed in Salmonella, the escape of these bacteria into the cytoplasm of infected macrophages.

Antigens, Bacterial↗
PubMed1993

Oligomerization of Escherichia coli haemolysin (HlyA) is involved in pore formation.

Coexpression of pairs of nonhaemolytic HlyA mutants in the recombination-deficient (recA) strain Escherichia coli HB101 resulted in a partial reconstitution of haemolytic activity, indicating that the mutation in one HlyA molecule can be complemented by the corresponding wild-type sequence in the other mutant HlyA molecule and vice versa. This suggests that two or more HlyA molecules aggregate prior to pore formation. Partial reconstitution of the haemolytic activity was obtained by the combined expression of a nonhaemolytic HlyA derivative containing a deletion of five repeat units in the repeat domain and several nonhaemolytic HlyA mutants affected in the pore-forming hydrophobic region. The simultaneous expression of two inactive mutant HlyA proteins affected in the region at which HlyA is covalently modified by HlyC and the repeat domain, respectively, resulted in a haemolytic phenotype on blood agar plates comparable to that of wild-type haemolysin. However, complementation was not possible between pairs of HlyA molecules containing site-directed mutations in the hydrophobic region and the modification region, respectively. In addition, no complementation was observed between HlyA mutants with specific mutations at different sites of the same functional domain, i.e. within the hydrophobic region, the modification region or the repeat domain. The aggregation of the HlyA molecules appears to take place after secretion, since no extracellular haemolytic activity was detected when a truncated but active HlyA lacking the C-terminal secretion sequence was expressed together with a nonhaemolytic but transport-competent HlyA mutant containing a deletion in the repeat domain.

Bacterial Proteins↗
PubMed1993

Listeria monocytogenes--a model system for studying the pathomechanisms of an intracellular microorganism.

Virulence of Listeria monocytogenes is determined by a cluster of five genes in the order plcA, hly, mpl, actA and plcB, which are coordinately regulated by a transcriptional activator, termed PrfA. The gene for PrfA is located in front of plcA. Mutations within each of these genes reduce the virulence considerably and render the mutants unable to properly multiply and/or spread within the infected host cells. Under growth-limiting conditions PrfA-dependent proteins are preferentially synthesised. These studies indicate the existence of additional PrfA-regulated proteins in L. monocytogenes. The synthesis of catalase, superoxide dismutase, LmaA and p60 is not under the control of PrfA. These proteins seem to be also associated with virulence of L. monocytogenes. P60-related proteins are found as major extracellular proteins in all Listeria species but only p60 of L. monocytogenes is able to restore the failure of R-mutants (exhibiting a drastically reduced synthesis of p60) to adhere to 3T6 mouse fibroblasts. Adherence of L. monocytogenes to the epithelial Caco-2 cells seem to be independent of p60. The p60 protein of L. monocytogenes differs characteristically from the p60-related proteins of the nonvirulent Listeria species.

Amino Acid Sequence↗
PubMed1993

Surface-associated, PrfA-regulated proteins of Listeria monocytogenes synthesized under stress conditions.

The expression of the five clustered genes of Listeria monocytogenes: plcA, hly, mpl, actA and plcB is under the control of the positive regulation factor PrfA. Listeriolysin, encoded by the hly gene, is the only prominent PrfA-controlled gene product observed when L. monocytogenes strain NCTC 7973 is cultured in a rich medium at 37 degrees C to the logarithmic growth phase. Stress conditions such as heat-shock or stationary culture conditions lead to the induction of additional PrfA-dependent proteins (PdPs): ActA (92 kDa), a 38 kDa protein of unknown function and a 34 kDa protein which probably represents PlcA. Under nutrient-stress conditions PdPs are preferentially synthesized and in addition to the already known PdPs at least five new, not yet functionally identified PdPs are detected. All PdPs are either secreted or are localized at the cell surface. Differences in the amount as well as the sizes of the PdPs are observed in different L. monocytogenes strains.

Animals↗
PubMed1993

Listeria ivanovii is capable of cell-to-cell spread involving actin polymerization.

Listeria ivanovii has been considered to be pathogenic to animals but has rarely been found associated with human infections. It has been claimed that L. ivanovii lacks the actA gene, which in L. monocytogenes encodes a protein required for interaction with host cell actin. Using fluorescence microscopy and electron microscopy, we demonstrate that L. ivanovii can invade mammalian cells, lyse the phagosomal membrane, polymerize host cell actin, reorganize actin to form tails, and spread from cell to cell. However, no DNA homologous to the actA gene could be detected by polymerase chain reaction. Further, L. ivanovii lacks the 90-kDa surface protein which in L. monocytogenes is encoded by actA. Despite the ability to spread from cell to cell, L. ivanovii differed significantly from L. monocytogenes in being unable to form plaques on monolayers of 3T3 fibroblast cells.

Actins↗
PubMed1993

The iap gene of Listeria monocytogenes is essential for cell viability, and its gene product, p60, has bacteriolytic activity.

Expression of the iap gene of Listeria monocytogenes in the L. monocytogenes rough mutant RIII and in Bacillus subtilis DB104 caused the disruption of the cell chains which these two strains normally form under exponential growth conditions. The p60 protein produced by L. monocytogenes and B. subtilis DB104 also exhibited bacteriolytic activity detected in denaturing polyacrylamide gels containing heat-killed Micrococcus lysodeikticus. Purification of the p60 protein led to aggregation of p60 and loss of the cell chain disruption and bacteriolytic activities. A cysteine residue in the C-terminal part of p60 which is conserved in all p60-like proteins from the other Listeria species seems to be essential for both activities. The iap gene could not be inactivated without a loss of cell viability, indicating that p60 is an essential housekeeping protein for L. monocytogenes and probably also for other Listeria species. These data suggest that p60 possesses a murein hydrolase activity required for a late step in cell division.

Amino Acid Sequence↗
PubMed1992

A gene encoding a superoxide dismutase of the facultative intracellular bacterium Listeria monocytogenes.

A gene (lmsod) encoding superoxide dismutase (SOD; EC 1.15.1.1) of the facultative intracellular pathogen, Listeria monocytogenes, was cloned by functional complementation of an SOD-deficient Escherichia coli mutant. The nucleotide sequence was determined and the deduced amino acid (aa) sequence (202 aa) showed close similarity to manganese-containing SOD's from other organisms. Subunits of the recombinant L. monocytogenes SOD (re-SOD) and of both E. coli SODs formed enzymatically active hybrid enzymes in vivo. DNA/DNA-hybridization experiments showed that this type of recombinant re-sod gene is conserved within the genus Listeria.

Amino Acid Sequence↗
PubMed1992

A novel bacterial virulence gene in Listeria monocytogenes required for host cell microfilament interaction with homology to the proline-rich region of vinculin.

The ability of Listeria monocytogenes to move within the cytosol of infected cells and their ability to infect adjacent cells is important in the development of infection foci leading to systemic disease. Interaction with the host cell microfilament system, particularly actin, appears to be the basis for propelling the bacteria through the host cell cytoplasm to generate the membraneous protrusions whereby cell-to-cell spread occurs. The actA locus of L.monocytogenes encodes a 90 kDa polypeptide that is a key component of bacterium-host cell microfilament interactions. Cloning of the actA gene allowed the identification of its gene product and permitted construction of an isogenic mutant strain defective in the production of the ActA polypeptide. Sequencing of the region encoding the actA gene revealed that it was located region encoding the actA gene revealed that it was located between the metalloprotease (mpl) and phosphatidylcholine-specific phospholipase C (plcB) genes. Within the cytoplasm of the infected cells, the mutant strain grew as microcolonies, was unable to accumulate actin following escape from the phagocytic compartment and was incapable of infecting adjacent cells. It was also dramatically less virulent, demonstrating that the capacity to move intracellularly and spread intercellularly is a key determinant of L.monocytogenes virulence. Like all other virulence factors described for this microorganism, expression of the ActA polypeptide is controlled by the PrfA regulator protein. The primary sequence of this protein appeared to be unique with no extended homology to known protein sequences. However, an internal repeat sequence showed strong regional homology to a sequence from within the hinge region of the cytoskeletal protein vinculin.

Actin Cytoskeleton↗
PubMed1992

A topological model for the haemolysin translocator protein HlyD.

A topological model for HlyD is proposed that is based on results obtained with gene fusions of lacZ and phoA to hlyD. Active HlyD-LacZ fusion proteins were only generated when lacZ was fused to hlyD within the first 180 bp (60 amino acids). HlyD-PhoA proteins exhibiting alkaline phosphatase (AP) activity were obtained when phoA was inserted into hlyD between nucleotides 262 (behind amino acid position 87) and 1405 (behind amino acid position 468, only 10 amino acids away from the C-terminus of HlyD). Active insertions of phoA into the middle region of hlyD were not observed on in vivo transposition but such fusions exhibiting AP activity could be constructed by in vitro techniques. A fusion protein that carried the PhoA part close to the C-terminal end of HlyD proved to be the most stable HlyD-PhoA fusion protein. In contrast to the other, rather unstable, HlyD-PhoA+ fusions, no proteolytic degradation product of this HlyD-PhoA protein was observed and nearly all the alkaline phosphatase activity was membrane bound. Protease accessibility and cell fractionation experiments indicated that the alkaline phosphatase moiety of this fusion protein was located in the periplasm as for all other HlyD-PhoA+ proteins. These data and computer-assisted predictions suggest a topological model for HlyD with the N-terminal 60 amino acids located in the cytoplasm, a single transmembrane segment from amino acids 60 to 80 and a large periplasmic region extending from amino acid 80 to the C-terminus.(ABSTRACT TRUNCATED AT 250 WORDS)

Alkaline Phosphatase↗
PubMed1992

Cloning of a superoxide dismutase gene from Listeria ivanovii by functional complementation in Escherichia coli and characterization of the gene product.

A gene encoding superoxide dismutase (EC 1.15.1.1., SOD) was isolated from a plasmid library of chromosomal DNA from Listeria ivanovii by functional complementation of an SOD-negative Escherichia coli host. The nucleotide sequence of the cloned gene was determined and contained an open reading frame which codes for a protein of 202 amino acid residues (calculated molecular weight 22755 Da including the amino-terminal methionine residue). Comparison of the deduced amino acid sequence of L. ivanovii SOD with previously reported SOD amino acid sequences revealed considerable homologies with Fe- and Mn-dependent SODs. Enzymatic analyses using cell lysates and the purified recombinant enzyme indicated that this SOD is manganese-dependent. The recombinant SOD accounted for up to 30% of the total soluble protein in recombinant E. coli and protected sodA sodB mutants against the toxic effects of paraquat. Subunits of the recombinant Listeria SOD and of both E. coli SODs formed enzymatically active hybrids in vivo.

Amino Acid Sequence↗
PubMed1992

Topological and functional studies on HlyB of Escherichia coli.

The topology of HlyB, a protein located in the inner membrane of Escherichia coli and involved in the secretion of alpha-haemolysin (HlyA), was determined by the generation of HlyB-PhoA and HlyB-LacZ fusion proteins. The data obtained by this biochemical method together with computer predictions suggest that HlyB is inserted in the cytoplasmic membrane by six stable hydrophobic, alpha-helical transmembrane segments. These segments extend from amino acid positions 158 to 432 of HlyB. The cytoplasmic loops between these transmembrane segments are relatively large and carry an excess of positively charged amino acids, while the periplasmic loops are rather small. In addition to these six transmembrane segments, two additional regions in the 78 N-terminal amino acids of HlyB appear to be also inserted in the cytoplasmic membrane. However, the association of these two segments with the cytoplasmic membrane seems to be less tight, since active PhoA and LacZ fusions were obtained by insertion into the same positions of these segments. A LacZ-HlyAs, fusion protein carrying, at the C-terminus of LacZ, the 60-amino acid signal sequence of HlyA was not secreted in the presence of HlyB/HlyD. However, transport of this fusion protein into the cytoplasmic membrane appeared to be initiated, as suggested by the tight association of this protein with the inner membrane. A similar close association of LacZ-HlyAs with the inner membrane was also observed in the presence of HlyB alone but not in its absence. These data suggest that HlyB recognizes the HlyA signal sequence and initiates the transport of HlyA into the membrane.

Alkaline Phosphatase↗
PubMed1992

Processing by OmpT of fusion proteins carrying the HlyA transport signal during secretion by the Escherichia coli hemolysin transport system.

A fusion gene (ces-hlyAs) was constructed by ligating the genetic information for the C-terminal 60 amino acids (hlyAs) of Escherichia coli hemolysin (HlyA) to the ces gene for a cholesterol esterase/lipase (CE) from a Pseudomonas species. Part (about 30%) of the expressed fusion protein CE-HlyAs was secreted in E. coli carrying hlyB and hlyD genes. Following the insertion between the reporter gene and hlyAs of a linker sequence that contains the information for potential cleavage sites for the outer membrane protease OmpT, two different fusion proteins (PhoA-HlyAs and CE-HlyAs) were shown to be cleaved by OmpT between the two parts during HlyB/HlyD-mediated secretion. Processed PhoA and CE accumulated in the supernatant. The efficiency of cleavage by OmpT was considerably improved by increased ompT gene dose. It was further shown that OmpT preferentially recognizes potential cleavage sites within the linker sequence.

Amino Acid Sequence↗
PubMed1992

Genetics of Escherichia coli uropathogenicity: analysis of the O6:K15:H31 isolate 536.

E. coli strain 536 (O6:K15:H31) isolated from a case of acute pyelonephritis, expresses S-fimbrial adhesins, P-related fimbriae, common type I fimbriae, and hemolysins. The respective chromosomally encoded determinants were cloned by constructing a genomic library of this strain. Furthermore, the strain produces the iron uptake substance, enterocheline, damages HeLa cells, and behaves in a serum-resistant mode. Genetic analysis of spontaneously arising non-hemolytic variants revealed that some of the virulence genes were physically linked to large unstable DNA regions, termed "pathogenicity islands", which were mapped in the respective positions on the E. coli K-12 linkage map. By comparing the wild type strain and mutants in in vitro and in vivo assays, virulence features have been evaluated. In addition, a regulatory cross talk between adhesin determinants was found for the wild-type isolate. This particular mode of virulence regulation is missing in the mutant strain.

Chromosome Mapping↗
PubMed1992

Haemolysin-derived synthetic peptides with pore-forming and haemolytic activity.

Escherichia coli haemolysin (Hlya) is a pore-forming protein which belongs to the family of 'Repeat-toxins' (RTX) (Lo et al., 1987; Lally et al., 1989; Kraig et al., 1990). A model for the pore-forming structure of HlyA has been proposed (Ludwig et al., 1991) which consists of eight transmembrane segments all present in this hydrophobic region of HlyA. We report here that two synthetic peptides of 10 and 8 amino acids in length (Pep1 and Pep2, respectively), which are derived from transmembrane segment V, are able to form pores in an artificial lipid bilayer. In addition, Pep1 exhibits strong haemolytic activity when tested on human red blood cells (HRBCs). The haemolytic activity of Pep1 and of E. coli haemolysin is completely inhibited by antibodies raised against Pep1.

Amino Acid Sequence↗
PubMed1992

Expression of bacterial cytotoxin genes in mammalian target cells.

We have studied the expression of the gene fragments encoding the enzymatically active portion of three bacterial cytotoxins: exotoxin A (ETA) of Pseudomonas aeruginosa, and pertussis toxin (PT) and adenylate cyclase toxin (CYA) of Bordetella pertussis, in sensitive mammalian target cells. Expression of active ETA and CYA was lethal to the producing cells and stable transfectants of Cos-1 cells containing the corresponding genes could not be obtained. The expression of the PTS1 subunit was tolerated by the producing mammalian cells. Since PT is cytotoxic because of ADP-ribosylation of G-proteins, we assume that the endogenously expressed PTS1 may not find the cellular target G proteins or PTS1 alone may not be sufficient for ADP-ribosylation of these proteins in vivo.

ADP Ribose Transferases↗
PubMed1992

Haemolysin of Escherichia coli: comparison of pore-forming properties between chromosome and plasmid-encoded haemolysins.

Lipid bilayer experiments were performed with chromosome-encoded haemolysin of Escherichia coli. The addition of the toxin to the aqueous phase bathing lipid bilayer membranes of asolectin resulted in the formation of transient ion-permeable channels with two states at small transmembrane voltages. One is a prestate (single-channel conductance 40 pS in 0.15 M KCl) of the open state, which had a single-channel conductance of 420 pS in 0.15 M KCl and a mean lifetime of 30 s. Membranes formed of pure lipids were rather inactive targets for this haemolysin. Experiments with different salts suggested that the haemolysin channel was highly cation-selective at neutral pH. The mobility sequence of the cations in the channel was similar if not identical to their mobility sequence in the aqueous phase. The single-channel data were consistent with a wide, water-filled channel with an estimated minimal diameter of about 1 nm. The pore-forming properties of chromosome-encoded haemolysin were compared with those of plasmid-encoded haemolysin. Both toxins share common features, oligomerize probably to form pores in lipid bilayer membranes. Both types of haemolysin channels have similar properties but different lifetimes.

Amino Acid Sequence↗