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At least 163 records · Page 9Linked to original sources
PubMed2003

Role of a highly conserved bacterial protein in outer membrane protein assembly.

After transport across the cytoplasmic membrane, bacterial outer membrane proteins are assembled into the outer membrane. Meningococcal Omp85 is a highly conserved protein in Gram-negative bacteria, and its homolog Toc75 is a component of the chloroplast protein-import machinery. Omp85 appeared to be essential for viability, and unassembled forms of various outer membrane proteins accumulated upon Omp85 depletion. Immunofluorescence microscopy revealed decreased surface exposure of outer membrane proteins, which was particularly apparent at the cell-division planes. Thus, Omp85 is likely to play a role in outer membrane protein assembly.

Amino Acid Sequence↗
PubMed1991

Bacterial protein toxins acting on intracellular targets.

A number of bacterial toxins act on targets located in the cytosol. Diphtheria toxin, Pseudomonas aeruginosa exotoxin A and shigella toxin inhibit protein synthesis by enzymatic inactivation of elongation factor 2 or the 60 S ribosomal subunit. These toxins enter the cells by receptor-mediated endocytosis, followed by translocation across the membranes of intracellular organelles. Also a number or toxins that are not cytocidal act on targets in the cytosol. A number of nontoxic bacterial proteins are able to modify enzymatically intracellular molecules. Some of these proteins could be considered for targeting to special cells followed by translocation to obtain defined physiological effects.

ADP Ribose Transferases↗
PubMed2000

The bacterial protein YopJ abrogates multiple signal transduction pathways that converge on the transcription factor CREB.

Bacterially encoded proteins are known to affect eukaryotic signalling pathways and thus cell growth and differentiation. The enteric pathogen Yersinia pseudotuberculosis (YP) can translocate Yersinia outer proteins (Yops) into eukaryotic cells. Recently, MKK proteins have been identified as tentative targets of YopJ-mediated inhibition of ligand receptor-dependent signal transduction in mammalian cells. These results prompted us to assess whether multiple signal transduction pathways and their downstream target genes would also be subject to regulation by YopJ. Here, we show that YopJ effectively blocks the lipopolysaccharide (LPS) receptor, the interleukin (IL)-1beta receptor and the UVC-induced activation of the transcription receptor cAMP response element-binding protein (CREB). In addition, by abrogating the phosphorylation of CREB and thus activating protein (AP)-1-dependent transcription, YopJ can block LPS-induced clonal expansion that is associated with an adaptive immune response. Thus, YopJ interferes with multiple pathways converging on the transcription factor CREB. Our data are discussed in the context of YopJ acting as an antagonist to circumvent innate and adaptive immune responses at multiple levels.

Bacterial Proteins↗
PubMed1998

An essential component of a novel bacterial protein export system with homologues in plastids and mitochondria.

Proteins are transported across the bacterial plasma membrane and the chloroplast thylakoid membrane by means of protein translocases that recognize N-terminal targeting signals in their cognate substrates. Transport of many of these proteins involves the well defined Sec apparatus that operates in both membranes. We describe here the identification of a novel component of a bacterial Sec-independent translocase. The system probably functions in a similar manner to a Sec-independent translocase in the thylakoid membrane, and substrates for both systems bear a characteristic twin-arginine motif in the targeting peptide. The translocase component is encoded in Escherichia coli by an unassigned reading frame, yigU, disruption of which blocks the export of at least five twin-Arg-containing precursor proteins that are predicted to bind redox cofactors, and hence fold, prior to translocation. The Sec pathway remains unaffected in the deletion strain. The gene has been designated tatC (for twin-arginine translocation), and we show that homologous genes are present in a range of bacteria, plastids, and mitochondria. These findings suggest a central role for TatC-type proteins in the translocation of tightly folded proteins across a spectrum of biological membranes.

Bacterial Proteins↗
PubMed1993

Release of lipid vesicle contents by the bacterial protein toxin alpha-haemolysin.

alpha-Haemolysin is a protein toxin (107 kDa) secreted by some pathogenic strains of E. coli. It binds to mammalian cell membranes, disrupting cellular activities and lysing cells. This paper describes the mechanism of alpha-haemolysin-induced membrane leakage, from experiments in which extrusion large unilamellar vesicles, loaded with fluorescent solutes, are treated with purified toxin. The results show that the toxin does not require of any membrane receptor to exert its activity, that vesicles become leaky following an 'all-or-none' mechanism, and that leakage occurs through a non-osmotic detergent-like bilayer disruption induced by the protein. Small pores formed by monomeric alpha-haemolysin, as described by other authors, do not appear to be related to the process of membrane disruption. Instead, the experimental data would be in agreement with the idea of oligomeric assemblies being required to produce release of solutes from a single vesicle.

Bacterial Proteins↗
PubMed2003

Molecular features of the cytolytic pore-forming bacterial protein toxins.

The repertoire of the cytolytic pore-forming protein toxins (PFT) comprises 81 identified members. The essential feature of these cytolysins is their capacity to provoke the formation of hydrophilic pores in the cytoplasmic membranes of target eukaryotic cells. This process results from the binding of the proteins on the cell surface, followed by their oligomerization which leads to the insertion of the oligomers into the membrane and formation of protein-lined channels. It impairs the osmotic balance of the cell and causes cytolysis. In this review the molecular aspects of a number of important PFT and their respective encoding structural genes will be briefly described.

Animals↗
PubMed1997

Bacterial protein secretion--a target for new antibiotics?

The heavy use of antibiotics over recent decades has resulted in widespread resistance of bacteria to many drugs. Overcoming resistance requires new approaches to antibiotic development, including the exploitation of new targets in the bacterial cell. Protein secretion is essential for bacterial cell growth and virulence, so it could be a suitable target for new therapeutic agents.

Anti-Bacterial Agents↗