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At least 253 records · Page 14Linked to original sources
PubMed2006

Protease inhibitors in bacteria: an emerging concept for the regulation of bacterial protein complexes?

Serine protease inhibitors (serpins), the antagonists of serine proteases, were unknown in the bacterial kingdom until recently. Kang et al. in this issue of Molecular Microbiology report the cloning and functional analysis of the three serpin genes from the thermophilic anaerobic bacterium Clostridium thermocellum. Two of the serpins contain a dockerin module for location in the extracellular hydrolytic multienzyme complex, the cellulosome. The susceptibility of cellulosome to proteolytic degradation and the presence of a serine protease in the same complex provoke speculation that protease inhibitor/protease pairs could play hitherto unrecognized roles in protein stability and regulation in bacteria.

Bacterial Proteins↗
PubMed1972

Correlation between rates of degradation of bacterial proteins in vivo and their sensitivity to proteases.

Experiments were undertaken to test whether the relative rates of degradation of proteins in vivo might correlate with their sensitivity to proteases. Various experimental conditions that promote degradation of proteins in Escherichia coli increased sensitivity of average cell proteins to trypsin or other endoproteases, including incorporation of several aminoacid analogs into the proteins, incorporation of puromycin into the polypeptide chain, or frequent errors in translation. Those abnormal proteins that were degraded most rapidly within the cell appear responsible for the increased protease sensitivity of the cell extract. Normal E. coli proteins that rapidly turn over in growing cells are, on the average, more sensitive to trypsin or Pronase than cell proteins that turn over more slowly. The inherent sensitivity of a protein to proteolytic digestion is thus a major determinant of protein half-lives in vivo.

Amino Acids↗
PubMed2006

Bacterial protein toxins and lipids: role in toxin targeting and activity.

All bacterial toxins, which globally are hydrophilic proteins, interact first with their target cells by recognizing a surface receptor, which is either a lipid or a lipid derivative, or another compound but in a lipid environment. Intracellular active toxins follow various trafficking pathways, the sorting of which is greatly dependent on the nature of the receptor, notably lipidic receptor or receptor embedded into a distinct environment such as lipid microdomains. Numerous other toxins act locally on cell membrane. Indeed, phospholipase activity is a common mechanism shared by several membrane-damaging toxins. In addition, many toxins active intracellularly or on cell membrane modulate host cell phospholipid pathways. Unusually, a few bacterial toxins require a lipid post-translational modification to be active. Thereby, lipids are obligate partners of bacterial toxins.

Bacterial Infections↗
PubMed2004

Translocation of bacterial proteins--an overview.

Recent progress in the understanding of the nature of the extraordinary variety of protein translocation systems, mainly in Gram negative bacteria, is reviewed. This takes us from the insertion of proteins into the inner membrane via the sophisticated Sec apparatus, the lethal injection of Type III proteins into host cells and on to the beautiful machine that assembles the flagellum. Attempts are made to establish some order, some common principles that might explain the variety and the complexity of some systems. The fundamentals considered are the nature of different transport signals, the nature of translocons (a wide variety of inner membrane types, outer membrane translocons are more conserved), the process of docking to translocons, the role of chaperones and the folding of transported proteins, the energetics of translocation, and prospects for future advances.

Bacterial Proteins↗
PubMed2004

Temperature regulates bacterial protein production: possible role in rosacea.

Facial skin temperature is higher for patients with rosacea. Papules and pustules might arise because bacteria behave differently at these warmer temperatures. We sought to: (1) compare bacteria from facial skin of patients with rosacea with that of control subjects; and (2) grow these bacteria at 30 degrees C and 37 degrees C to compare growth curves and secreted proteins. Bacteria isolated from pustules/skin surfaces of patients with rosacea and skin surfaces of control subjects were identified and cultured at 37 degrees C and 30 degrees C. Secreted proteins were separated by electrophoresis. We found that Staphylococcus epidermidis isolated from patients with rosacea was consistently beta-hemolytic, whereas that from control subjects were nonhemolytic. Bacteria from patients with rosacea grew at the same rate and to the same stationary phase whether cultured at 37 degrees C or 30 degrees C. Isolates from patients with rosacea secreted more proteins, and generally more of each protein at 37 degrees C compared with 30 degrees C. In conclusion, bacteria isolated from patients with rosacea secrete different proteins and different amounts of protein at different temperatures.

Bacterial Proteins↗
PubMed1993

A human cDNA corresponding to a gene overexpressed during cell proliferation encodes a product sharing homology with amoebic and bacterial proteins.

A clone, designated pag, was isolated by differential screening of cDNA libraries made from the untransformed and ras-transformed human mammary epithelial cell line HBL100. This cDNA corresponds to a gene constitutively expressed in most human cells which is induced to higher levels upon serum stimulation in untransformed and ras-transformed HBL100 cells. However, the abundance of the pag transcript is approximately 3-fold higher in transformed as compared to untransformed cells after 7-15 h of serum stimulation. In the promyelocytic leukemia cell line HL60 induced to differentiate the level of pag mRNA starts to decrease between 48 and 72 h following induction. During this period, which represents the commitment phase of differentiation, HL60 cells cease to proliferate. Therefore, in HBL100 and HL60 cells, higher levels of pag gene expression are correlated with cell proliferation. The pag cDNA codes for a 22-kDa protein, devoid of known consensus motifs, and shares 66% homology with a murine gene product (MER5) that is preferentially expressed in erythroleukemia cells during the early period of cell differentiation. In addition, the pag gene product shares approximately 50% identity with a 29-kDa surface antigen of Entamoeba histolytica and a 26-kDa antigen of Helicobacter pylori. Distant relationship was also found with other prokaryotic proteins. The pag cDNA hybridizes to multiple sequences within human and other mammalian genomes and to fewer sequences in chicken and Saccharomyces cerevisiae. Although a true relationship between eukaryotic and prokaryotic genes is difficult to establish, the conservation of pag gene sequences throughout Eukaryotae rather suggests that the pag locus belongs to a new class of genes encoding highly conserved proteins.

Amino Acid Sequence↗
PubMed2006

A translocated bacterial protein protects vascular endothelial cells from apoptosis.

The modulation of host cell apoptosis by bacterial pathogens is of critical importance for the outcome of the infection process. The capacity of Bartonella henselae and B. quintana to cause vascular tumor formation in immunocompromised patients is linked to the inhibition of vascular endothelial cell (EC) apoptosis. Here, we show that translocation of BepA, a type IV secretion (T4S) substrate, is necessary and sufficient to inhibit EC apoptosis. Ectopic expression in ECs allowed mapping of the anti-apoptotic activity of BepA to the Bep intracellular delivery domain, which, as part of the signal for T4S, is conserved in other T4S substrates. The anti-apoptotic activity appeared to be limited to BepA orthologs of B. henselae and B. quintana and correlated with (i) protein localization to the host cell plasma membrane, (ii) elevated levels of intracellular cyclic adenosine monophosphate (cAMP), and (iii) increased expression of cAMP-responsive genes. The pharmacological elevation of cAMP levels protected ECs from apoptosis, indicating that BepA mediates anti-apoptosis by heightening cAMP levels by a plasma membrane-associated mechanism. Finally, we demonstrate that BepA mediates protection of ECs against apoptosis triggered by cytotoxic T lymphocytes, suggesting a physiological context in which the anti-apoptotic activity of BepA contributes to tumor formation in the chronically infected vascular endothelium.

Apoptosis↗