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At least 37 records · Page 2Linked to original sources
PubMed2005

FtsZ and the division of prokaryotic cells and organelles.

Binary fission of many prokaryotes as well as some eukaryotic organelles depends on the FtsZ protein, which self-assembles into a membrane-associated ring structure early in the division process. FtsZ is homologous to tubulin, the building block of the microtubule cytoskeleton in eukaryotes. Recent advances in genomics and cell-imaging techniques have paved the way for the remarkable progress in our understanding of fission in bacteria and organelles.

Bacteria↗
PubMed2003

Temporal and spatial regulation in prokaryotic cell cycle progression and development.

Bacteria exhibit a high degree of intracellular organization, both in the timing of essential processes and in the placement of the chromosome, the division site, and individual structural and regulatory proteins. We examine the temporal and spatial regulation of the Caulobacter cell cycle, bacterial chromosome segregation and cytokinesis, and Bacillus subtilis sporulation. Mechanisms that control timing of cell cycle and developmental events include transcriptional cascades, regulated phosphorylation and proteolysis of signal transduction proteins, transient genetic asymmetry, and intercellular communication. Surprisingly, many signal transduction proteins are dynamically localized to specific subcellular addresses during the cell division cycle and sporulation, and proper localization is essential for their function. The Min proteins that govern division site selection in Escherichia coli may be the first example of a system that generates positional information de novo.

Bacillus subtilis↗
PubMed2005

Phenotypic alteration and target gene identification using combinatorial libraries of zinc finger proteins in prokaryotic cells.

We have developed a method with prokaryotic organisms that uses randomized libraries of zinc finger-containing artificial transcription factors to induce phenotypic variations and to identify genes involved in the generation of a specific phenotype of interest. Combining chromatin immunoprecipitation experiments and in silico prediction of target DNA binding sequences for the artificial transcription factors, we identified ubiX, whose down-regulation correlates with the thermotolerance phenotype in Escherichia coli. Our results show that randomized libraries of artificial transcription factors are powerful tools for functional genomic studies.

Amino Acid Sequence↗
PubMedDate not supplied

[Magnet sensitive inclusion in procaryotic cells].

Prokaryotic cells may contain one of two types of magnetic intracellular structures, either crystalline magnetosomes or noncrystalline magnetic inclusions. In a magnetic field, the locomotor behavior of cells containing magnetosomes is categorized as magnetotaxis, whereas noncrystalline magnetic inclusions cause a passive attraction of cells containing such inclusions to a magnet. The review considers the distribution, structure, and function of both types of magnetic particles in prokaryotic cells.

Bacteria↗
PubMed1999

Chromosome segregation during the prokaryotic cell division cycle.

Recent work has dramatically changed our view of chromosome segregation in bacteria. Rather than being a passive process, it involves rapid movement of parts of the circular chromosome. Several genes involved in chromosome segregation have been identified, and the analysis of their functions and intracellular localization are beginning to shed light on the mechanisms that ensure efficient chromosome segregation.

Bacillus subtilis↗
PubMed2003

The Enterococcus faecalis cytolysin: a novel toxin active against eukaryotic and prokaryotic cells.

The enterococcal cytolysin, a two-peptide lytic system, is a divergent relative of a large family of toxins and bacteriocins secreted by pathogenic and non-pathogenic Gram-positive bacteria. This family includes the lantibiotics and streptolysin S. The enterococcal cytolysin is of interest because its activities enhance enterococcal virulence in infection models and, in epidemiological studies, it has been associated with patient mortality. The cytolysin is lethal for a broad range of prokaryotic and eukaryotic cells, and this activity requires two non-identical, post-translationally modified peptides. The smaller of the two peptides also plays a role in a quorum-sensing autoinduction of the cytolysin operon. As a trait that is present in particularly virulent strains of Enterococcus faecalis, including strains that are resistant to multiple antibiotics, it serves as a model for testing the value of developing new virulence-targeting therapeutics. Further, because of the interest in small membrane active peptides as therapeutics themselves, studies of the molecular structure/activity relationships for the cytolysin peptides are providing insights into the physical basis for prokaryotic versus eukaryotic cell targeting.

Animals↗
PubMedDate not supplied

[Characteristics of the stoichiometric regulation of glycolysis in prokaryotic cells. A model].

A model is developed to investigate the steady state of the glycolytic system of procaryotic cells which have the hexose transport into the cell coupled with phosphoenolpyruvic acid-dependent phosphorylation. Analysis of the model shows that this phosphorylation results: 1) in stoichiometric connection between the rate of hexose consumption and the utilization of ATP and 2) the stoichiometric positive feedback. The latter can be the cause of bistability, oscillations and other nonlinear phenomena.

Bacteria↗
PubMed2004

How do prokaryotic cells cycle?

This issue of Current Biology features five reviews covering various key aspects of the eukaryotic cell cycle. The topics include initiation of chromosome replication, assembly of the mitotic spindle, cytokinesis, the regulation of cell-cycle progression, and cell-cycle modeling, focusing mainly on budding yeast, fission yeast and animal cell model systems. The reviews underscore common themes as well as key differences in the way these processes are carried out and regulated among the different model organisms. Consequently, an important question is how cell-cycle mechanisms and controls have evolved, particularly in the broader perspective of the three domains of life.

Bacterial Proteins↗
PubMed2003

Pathogenicity mechanisms of prokaryotic cells: an evolutionary view.

The success of pathogenic microbes depends on their ability to colonize host tissues and to counter host defense mechanisms. Microorganisms can produce overwhelming infection because of their relatively short generation times, and because they have evolved powerful mechanisms for generating phenotypic diversity as an efficient strategy for adapting to rapidly responding immune system defenses and the broad range of polymorphisms characteristic of different host tissues. Bacterial evolution may not be a continuous process, but more of a succession of temporally spaced major events. These events cause a non-gradual sequence of adaptations to a given environment. The pathogenicity islands are genetically unstable elements, and many of the genes coding for the adhesins, toxins and other virulence factors are present in pathogenicity islands, which almost certainly had former lives as accessory elements or as parts thereof, or were borne on functional accessory elements. Novel genes are also acquired by transduction (mediated by bacteriophages, plasmids or transposons), by conjugation (DNA transfer between cells) or by transformation (natural DNA uptake). Horizontal gene transfer from other species is a major source of variation and is fundamental to the genetic theory of adaptive evolution in prokaryotes.

Bacteria↗
PubMed2003

Two Dictyostelium orthologs of the prokaryotic cell division protein FtsZ localize to mitochondria and are required for the maintenance of normal mitochondrial morphology.

In bacteria, the protein FtsZ is the principal component of a ring that constricts the cell at division. Though all mitochondria probably arose through a single, ancient bacterial endosymbiosis, the mitochondria of only certain protists appear to have retained FtsZ, and the protein is absent from the mitochondria of fungi, animals, and higher plants. We have investigated the role that FtsZ plays in mitochondrial division in the genetically tractable protist Dictyostelium discoideum, which has two nuclearly encoded FtsZs, FszA and FszB, that are targeted to the inside of mitochondria. In most wild-type amoebae, the mitochondria are spherical or rod-shaped, but in fsz-null mutants they become elongated into tubules, indicating that a decrease in mitochondrial division has occurred. In support of this role in organelle division, antibodies to FszA and FszA-green fluorescent protein (GFP) show belts and puncta at multiple places along the mitochondria, which may define future or recent sites of division. FszB-GFP, in contrast, locates to an electron-dense, submitochondrial body usually located at one end of the organelle, but how it functions during division is unclear. This is the first demonstration of two differentially localized FtsZs within the one organelle, and it points to a divergence in the roles of these two proteins.

Amino Acid Motifs↗
PubMed1989

Evidence for a membrane-associated GTP-binding protein in Stigmatella aurantiaca, a prokaryotic cell.

Signal transducing G proteins are present in all eukaryotic cells, but they have not been found in prokaryotes so far. Myxobacteria, especially Stigmatella aurantiaca, are prokaryotic organisms able to exchange signals. Moreover, they exhibit an active phosphoinositide metabolism, whose intensity is dependent on the physiological state of the cell. Therefore G proteins potentially involved in the activation of phospholipid metabolism or any other event stimulated by external signals were looked for in S. aurantiaca membranes. Using a photoaffinity technique based on cross-linking of radioactive GTP to membrane-associated proteins under UV irradiation, only one major band in the range of 54 kDa was detected. This GTP-binding protein present specifically in membrane preparations binds also GDP, whereas it does not react with other nucleotides, such as ATP, UTP and CTP. The membrane-bound G protein of S. aurantiaca needs further characterization but could be homologous to G alpha subunits found in cytoplasmic membranes of eukaryotes.

Affinity Labels↗
PubMed1984

Occurrence of S-adenosylhomocysteine hydrolase in prokaryote cells. Characterization of the enzyme from Alcaligenes faecalis and role of the enzyme in the activated methyl cycle.

The occurrence of S-adenosylhomocysteine hydrolase (EC 3.3.1.1) was found in a variety of prokaryotes. These prokaryotes did not exhibit any activities of S-adenosylhomocysteine nucleosidase (EC 3.2.2.9) and S-ribosyl-homocysteine hydrolase (EC 3.3.1.3), which had been the generally accepted prokaryote enzymes for the regeneration of free homocysteine from S-adenosylhomocysteine in the activated methyl cycle. In these prokaryotes S-adenosylhomocysteine hydrolase was suggested to be the only enzyme functioning for the regeneration of free homocysteine by enzymological and immunochemical studies. S-Adenosylhomocysteine hydrolase was purified and crystallized from cells of a prokaryote, Alcaligenes faecalis. The purified enzyme was found to be homogeneous on ultracentrifugation and gel electrophoresis. Its relative molecular mass is approximately 280 000 and it is composed of six identical subunits with a Mr of approximately 48 000. The NH2-terminal and COOH-terminal amino acids are lysine and tyrosine respectively. The enzyme contains 6 mol NAD/mol. Some nucleosides, such as formycin A, nebularine, adenosine N1-oxide and so on, are able to substitute for adenosine yielding the corresponding S-nucleosidylhomocysteine congeners. Modification of the 5'-hydroxymethyl group in adenosine leads to the most potent inhibition of the thioether formation of homocysteine with adenosine. The enzyme from A. faecalis has some immunological similarities to other prokaryote S-adenosylhomocysteine hydrolases, but is different from the enzymes of animal sources.

Adenosylhomocysteinase↗
PubMed2003

A search method for homologs of small proteins. Ubiquitin-like proteins in prokaryotic cells?

The question of protein homology versus analogy arises when proteins share a common function or a common structural fold without any statistically significant amino acid sequence similarity. Even though two or more proteins do not have similar sequences but share a common fold and the same or closely related function, they are assumed to be homologs, descendant from a common ancestor. The problem of homolog identification is compounded in the case of proteins of 100 or less amino acids. This is due to a limited number of basic single domain folds and to a likelihood of identifying by chance sequence similarity. The latter arises from two conditions: first, any search of the currently very large protein database is likely to identify short regions of chance match; secondly, a direct sequence comparison among a small set of short proteins sharing a similar fold can detect many similar patterns of hydrophobicity even if proteins do not descend from a common ancestor. In an effort to identify distant homologs of the many ubiquitin proteins, we have developed a combined structure and sequence similarity approach that attempts to overcome the above limitations of homolog identification. This approach results in the identification of 90 probable ubiquitin-related proteins, including examples from the two prokaryotic domains of life, Archaea and Bacteria.

Amino Acid Sequence↗