Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Myxococcus”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 829 records · Page 46Linked to original sources
PubMed1995

Nm23/nucleoside diphosphate kinase: toward a structural and biochemical understanding of its biological functions.

The nm23 gene, a putative metastasis suppressor gene, was originally identified by its reduced expression in highly metastatic K-1735 murine melanoma cell lines, as compared to related, low metastatic melanoma cell lines. Transfection of nm23 cDNA has been reported to suppress malignant progression in Drosophila and mammalian cells. Highly conserved homologues of nm23 have been found in organisms ranging from the prokaryote Myxococcus xanthus to Drosophila, where the gene is involved in normal development and differentiation. The product of the nm23 gene exhibits a nucleoside diphosphate kinase activity, yet the nucleoside diphosphate kinase activity of Nm23 does not correlate with its apparent biological functions. We review recent cellular, genetic, biochemical and X-ray crystallographic data to formulate and evaluate hypotheses concerning the molecular mechanism of nm23 action.

Animals↗
PubMed2002

Classification of the caspase-hemoglobinase fold: detection of new families and implications for the origin of the eukaryotic separins.

A comprehensive sequence and structural comparative analysis of the caspase-hemoglobinase protein fold resulted in the delineation of the minimal structural core of the protease domain and the identification of numerous, previously undetected members, including a new protease family typified by the HetF protein from the cyanobacterium Nostoc. The first bacterial homologs of legumains and hemoglobinases were also identified. Most proteins containing this fold are known or predicted to be active proteases, but multiple, independent inactivations were noticed in nearly all lineages. Together with the tendency of caspase-related proteases to form intramolecular or intermolecular dimers, this suggests a widespread regulatory role for the inactive forms. A classification of the caspase-hemoglobinase fold was developed to reflect the inferred evolutionary relationships between the constituent protein families. Proteins containing this domain were so far detected almost exclusively in bacteria and eukaryotes. This analysis indicates that caspase-hemoglobinase-fold proteases and their inactivated derivatives are widespread in diverse bacteria, particularly those with a complex development, such as Streptomyces, Anabaena, Mesorhizobium, and Myxococcus. The eukaryotic separin family was shown to be most closely related to the mainly prokaryotic HetF family. The phyletic patterns and evolutionary relationships between these proteins suggest that they probably were acquired by eukaryotes from bacteria during the primary, promitochondrial endosymbiosis. A similar scenario, supported by phylogenetic analysis, seems to apply to metacaspases and paracaspases, with the latter, perhaps, being acquired in an independent horizontal transfer to the eukaryotes. The acquisition of the caspase-hemoglobinase-fold domains by eukaryotes might have been critical in the evolution of important eukaryotic processes, such as mitosis and programmed cell death.

Amino Acid Sequence↗
PubMed1998

Purification of and kinetic studies on a cloned protoporphyrinogen oxidase from the aerobic bacterium Bacillus subtilis.

The previously cloned and expressed protoporphyrinogen oxidase from Bacillus subtilis has been purified to homogeneity by Ni2+ affinity chromatography using a His6 tag and characterized. The enzyme has a molecular weight of approximately 56,000 daltons, a pI of 7.5, a pH optimum (protoporphyrinogen) of 8.7, and a noncovalently bound flavine adenine dinucleotide cofactor. The Michaelis constants (Km) for protoporphyrinogen-IX, coproporphyrinogen-III, and mesoporphyrinogen-IX are 1.0, 5.29, and 4.92 microM, respectively. Polyclonal antibody to B. subtilis protoporphyrinogen oxidase demonstrated weak cross-reactivity with both human and Myxococcus xanthus protoporphyrinogen oxidase. B. subtilis protoporphyrinogen oxidase is not inhibited by the diphenyl ether herbicide acifluorfen at 100 microM and is weakly inhibited by methylacifluorfen at the same concentration. Bilirubin, biliverdin, and hemin are all competitive inhibitors of this enzyme.

Aerobiosis↗
PubMed1995

The crystal structure of a human nucleoside diphosphate kinase, NM23-H2.

The 2.8 A resolution X-ray structure of NM23-H2 has been determined by molecular replacement using the structure of Myxococcus xanthus nucleoside diphosphate (NDP) kinase. NM23-H2 is a human NDP kinase. The enzyme catalyses phosphoryl transfer, binds DNA, and can activate the transcription of the c-myc oncogene in vitro. NM23 has also been reported to be a suppressor of metastasis in some types of tumours. Whereas the M. xanthus NDP kinase is a tetramer, NM23-H2 is a hexamer. The fold of NM23-H2 is identical to the fold of other NDP kinases. Two antiparallel helices joined by a turn form one edge of the nucleotide binding cleft. This region moves in a hinge-like fashion in response to substrate binding and crystal packing forces. Additional differences in conformation among the NDP kinases are principally in regions involved in protein-protein contacts within the oligomers. The only protein-protein interaction conserved among all NDP kinases is a dimeric interaction. Several mutations of NM23-H2 have been detected in tumour tissues. These mutations do not involve residues interacting with the substrates, and probably destabilise the enzyme without directly affecting the catalytic activity. Low level phosphorylation of serines has been reported for NM23 both in vitro and in vivo. The structure of the hexamer indicates that two serine residues that have been reported as being phosphorylated, Ser44 and Ser122, are on the surface of the hexamer, and are likely to be phosphorylated by exogenous kinases. In contrast, Ser120 is buried, and is most likely phosphorylated by a direct transfer from the phosphohistidine intermediate of the reaction mechanism.

Amino Acid Sequence↗
PubMed2001

Solution structure, backbone dynamics and chitin binding of the anti-fungal protein from Streptomyces tendae TU901.

AFP1 is a recently discovered anti-fungal, chitin-binding protein from Streptomyces tendae Tü901. Mature AFP1 comprises 86 residues and exhibits limited sequence similarity to the cellulose-binding domains of bacterial cellulases and xylanases. No similarity to the Cys and Gly-rich domains of plant chitin-binding proteins (e.g. agglutinins, lectins, hevein) is observed. AFP1 is the first chitin-binding protein from a bacterium for which anti-fungal activity was shown. Here, we report the three-dimensional solution structure of AFP1, determined by nuclear magnetic resonance spectroscopy. The protein contains two antiparallel beta-sheets (five and four beta-strands each), that pack against each other in a parallel beta-sandwich. This type of architecture is conserved in the functionally related family II of cellulose-binding domains, albeit with different connectivity. A similar fold is also observed in other unrelated proteins (spore coat protein from Myxococcus xanthus, beta-B2 and gamma-B crystallins from Bos taurus, canavalin from Jack bean). AFP1 is therefore classified as a new member of the betagamma-crystallin superfamily. The dynamics of the protein was characterized by NMR using amide 15N relaxation and solvent exchange data. We demonstrate that the protein exhibits an axially symmetric (oblate-like) rotational diffusion tensor whose principal axis coincides to within 15 degrees with that of the inertial tensor. After completion of the present structure of AFP1, an identical fold was reported for a Streptomyces killer toxin-like protein. Based on sequence comparisons and clustering of conserved residues on the protein surface for different cellulose and chitin-binding proteins, we postulate a putative sugar-binding site for AFP1. The inability of the protein to bind short chitin fragments suggests that certain particular architectural features of the solid chitin surface are crucial for the interaction.

Amino Acid Sequence↗
PubMed1983

In situ transposon replacement and isolation of a spontaneous tandem genetic duplication.

Using a specialized transducing P1 phage carrying an insertion of Tn5-132, an insertion of Tn5-wt in the chromosome of Myxococcus xanthus, which codes for resistance to kanamycin, can be replaced with one of Tn5-132, which codes for resistance to tetracycline. That Tn5-132 in the daughter is inserted at the same location in the chromosome as Tn5-wt was in the parent was shown by a variety of physical and genetic tests. Southern blot hybridizations of restriction digests of daughter and parent DNAs probed for sequences homologous to Tn5 show that the physical location is the same. When KmR was transduced from the parent to the TcR daughter by the generalized transducing myxophage Mx4 or Mx8, all the transductants were TcS. Likewise, when the daughter was used as donor, TcR transductants of its KmR parent were KmS. Flanking markers that were linked to KmR in the parent were linked to TcR in the daughter. Spontaneous tandem genetic duplications of portions of bacterial chromosomes can be trapped by transducing a selectable marker from a donor to a recipient that has a different selectable marker at the same genetic location and selecting transductants with both markers. Using Tc-replacement, this technique can be applied to any region of the chromosome. We used it to isolate a spontaneous tandem duplication of part of the M. xanthus chromosome. The duplication was characterized by Southern blot hybridizations probed for Tn5-homologous DNA. It was also shown to be unstable by quantitation of loss of drug resistance. Transduction of the novel joint led to reconstruction of the duplication in the recipient strain. All these tests gave results consistent with the proposed structure. The methods described here are applicable to any bacterium into which transposons can be introduced, and for which some means of genetic exchange is available.

DNA Transposable Elements↗
PubMed1978

Myxobacterial slime and proteolytic activity.

An extracellular protein-polysaccharide-lipide (PPL) complex from exponentially growing cultures of Myxococcus virescens was purified by phosphate precipitation and gel chromatography. The high molecular weight slime polymer appeared homogenous upon isoelectric focusing. The PPL complex exhibited proteolytic activity against gelatin and the activity was only partly reduced by heat treatment. The function of the slime polymer as protein denatured was studied. The complex formed micelles similar to anionic detergents and it inhibited the precipitation and coagulation of proteins by trichloroacetic acid. Lysozyme was totally inactivated when treated with the PPL complex. By gel chromatography binding studies, the PPL complex was found to bind lysozyme in the ratio of 1 to 5.8 (w/w). After separation of added protein from the complex the anticoagulation effect on the protein remained. The biological function of the PPL complex was demonstrated with hemoglobin. When all susceptible peptide bonds in PPL-treated hemoglobin were hydrolyzed by trypsin only 20% in the urea-denatured protein were attacked. The combined role of slime and proteolytic activity is discussed.

Bacterial Proteins↗
PubMed1980

Bacteriophage K7, a double stranded DNA phage that infects strains of Escherichia coli harbouring drug resistance factors of incompatability group W.

Bacteriophage K7 is specific for Escherichia coli strains harbouring R factors of incompatability group W, including hybrid coliphage P1-Myxococcus virescens plasmids. The phage has an unusual morphology with an isometric head and long tail of variable length. The tail lengths appear to fall into classes corresoonsing to simple multimers of a unit length. Partially purified lysates of the phage include material that may represent phage particles in the process of biogenesis and other material demonstrating attachment of phage to cell envelope. Newly released phage DNA contains single standed ends. In the course of work. E. coli strains that harbour R factor Sa were found to be apparently restrictive.

Coliphages↗
PubMed1990

Evolution of a protein superfamily: relationships between vertebrate lens crystallins and microorganism dormancy proteins.

A search of sequence databases shows that spherulin 3a, an encystment-specific protein of Physarum polycephalum, is probably structurally related to the beta- and gamma-crystallins, vertebrate ocular lens proteins, and to Protein S, a sporulation-specific protein of Myxococcus xanthus. The beta- and gamma-crystallins have two similar domains thought to have arisen by two successive gene duplication and fusion events. Molecular modeling confirms that spherulin 3a has all the characteristics required to adopt the tertiary structure of a single gamma-crystallin domain. The structure of spherulin 3a thus illustrates an earlier stage in the evolution of this protein superfamily. The relationship of beta- and gamma-crystallins to spherulin 3a and Protein S suggests that the lens proteins were derived from an ancestor with a role in stress-response, perhaps a response to osmotic stress.

Amino Acid Sequence↗
PubMed2006

Two continuum models for the spreading of myxobacteria swarms.

We analyze the phenomenon of spreading of a Myxococcus xanthus bacterial colony on plates coated with nutrient. The bacteria spread by gliding on the surface. In the first few hours, cell growth is irrelevant to colony spread. In this case, bacteria spread through peninsular protrusions from the edge of the initial colony. We analyze the diffusion through the narrowing reticulum of cells on the surface mathematically and derive formulae for the spreading rates. On the time scale of tens of hours, effective diffusion of the bacteria, combined with cell division and growth, causes a constant linear increase in the colony's radius. Mathematical analysis and numerical solution of reaction-diffusion equations describing the bacterial and nutrient dynamics demonstrate that, in this regime, the spreading rate is proportional to the square root of both the effective diffusion coefficient and the nutrient concentration. The model predictions agree with the data on spreading rate dependence on the type of gliding motility.

Mathematics↗
PubMed1992

The amino acid sequence of nucleoside diphosphate kinase I from spinach leaves, as deduced from the cDNA sequence.

The primary structure of nucleoside diphosphate (NDP) kinase from spinach leaves has been deduced from its cDNA sequence. A lambda gt 11 cDNA library derived from spinach leaves was screened using an antibody against NDP kinase I, which we previously purified to electrophoretic homogeneity (T. Nomura, T. Fukui, and A. Ichikawa, 1991, Biochim. Biophys. Acta 1077, 47-55). The cDNA sequences of positive clones contained the amino acid coding region (444 base pairs) for NDP kinase I as well as 5' and 3' noncoding regions of 33 and 361 base pairs, respectively. The cDNAs hybridized to a 1.1-kb mRNA. NDP kinase I contains 148 amino acid residues with a molecular mass of 16,305, which is in excellent agreement with that of the purified enzyme (16 kDa). Homology was found between the sequence of spinach NDP kinase I and those of the rat, Myxococcus xanthus, and Dictyostelium discoideum NDP kinases, as well as the human Nm23-gene product and the awd protein of Drosophila melanogaster.

Amino Acid Sequence↗
PubMed1975

Aspartokinase isoenzymes of the fruiting myxobacterium Myxoccus xanthus.

Two isoenzymes of aspartokinase can be found in extracts of the differentiating bacterium Myxococcus xanthus. Aspartokinase I is repressed by L-lysine and feedback is inhibited by meso-diaminopimelate and by low concentrations of L-lysine. However, the inhibition by L-lysine is no longer observed at high concentration of this amino acid. Aspartokinase II is repressed and feedback inhibited specifically by L-threonine. Both enzymes are stimulated significantly by L-methionine and L-isoleucine; the effect is greater with aspartokinase I. The role of these enzymes in relation to growth conditions of the organism is discussed and a correlation with life cycle activity is indicated.

Aspartate Kinase↗
PubMed1990

Anticoagulant activity of a bacterial glycopeptide.

The anticoagulant properties of myxalin, a glycopeptide secreted by a Gram negative bacterium strain (Myxococcus xanthus) are studied and compared to those of heparin. This soluble material exhibits an anticoagulant activity which implies the inhibition of some serine proteases, thrombin and factor Xa. In the presence of normal and antithrombin III-depleted plasma, myxalin inhibits the amidolytic activity of thrombin on synthetic chromogenic substrate as a function of its concentration, but fails to increase thrombin inactivation significantly in the presence of purified AT III. However, crossed immunoelectrophoresis data suggests that its antithrombi effect is mainly mediated by binding to the enzyme, rather than to AT III and probably differs from the catalytic activity of heparin which requires the presence of AT III. The anticoagulant process occurs without degradation of fibrinogen and can be neutralized by protamine.

Anticoagulants↗
PubMed1991

Sequence of hrdB, an essential gene encoding sigma-like transcription factor of Streptomyces coelicolor A3(2): homology to principal sigma factors.

The complete nucleotide sequence of the hrdB gene, an essential gene of Streptomyces coelicolor A3(2), indicates the presence of an open reading frame encoding a putative polypeptide of 442 amino acid (aa) residues with an Mr of 48,412. The principal sigma-like transcriptional factor of S. coelicolor (HrdB) protein showed an extensive aa sequence homology with the known principal sigma factors of Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Myxococcus xanthus. The degree of sequence similarity between HrdB protein and the known principal sigma factors was distinct from that observed between the principal sigma factors and the alternative (minor) sigma factors. Essentially all of the functional domains proposed for the principal sigma factor of E. coli were conserved in HrdB protein. The putative sigma factor, HrdB, like that of B. subtilis had a short internal nonconserved region, which might be characteristic of Gram+ species.

Amino Acid Sequence↗
PubMed1994

Cloning and characterization of the gene encoding the major sigma factor of Stigmatella aurantiaca.

The gene (sigA) encoding the major sigma factor of the myxobacterium, Stigmatella aurantiaca, was cloned and sequenced. The deduced polypeptide contains 706 amino acids (aa) and has a deduced M(r) of 79,910. It exhibits four different aa sequence motifs which correlate with the conserved domains of the major sigma factors of Myxococcus xanthus (sigma 80), Escherichia coli (sigma 70) and Bacillus subtilis (sigma 43). The sigma factor (sigma A) was detected in crude lysates of vegetative cells and in cells of different developmental stages from S. aurantiaca with an antiserum to M. xanthus sigma 80 by Western blot analysis. The SigA polypeptide copurified with RNA polymerase from vegetative S. aurantiaca cells. The aa sequence of its N terminus matches a sequence located 25 codons downstream from the proposed start codon. The sigA gene was expressed in E. coli and the corresponding gene product cross-reacted with the SigA antiserum as a polypeptide of 100 kDa, which is identical in size to the sigma A detected in vegetative cells of S. aurantiaca.

Amino Acid Sequence↗
PubMed1989

Bactericidal and bacteriolytic action of peptide antibiotic AS-48 against gram-positive and gram-negative bacteria and other organisms.

A purified peptide antibiotic AS-48 from Streptococcus faecalis spp liquiefaciens S-48 exerted a bactericidal mode of action against most Gram-positive and many Gram-negative bacteria tested. In many Gram-positive bacteria and the two Myxococcus species assayed, a bacteriolytic effect, as a consequence of primary lesions, was also observed. In general, the Gram-negative bacteria were more resistant to AS-48. Escherichia coli protoplasts showed increased sensitivity and those of a resistant yeast. Saccharomyces cerevisiae 3.2, became sensitive. These data suggest that resistance is related to the cell wall structure. AS-48 adsorbed rapidly to cell walls and cytoplasmic membranes of sensitive and resistant cells. Adsorption to cytoplasmic membranes involved complete neutralization of AS-48.

Adsorption↗
PubMed2005

Bioinformatics, genomics and evolution of non-flagellar type-III secretion systems: a Darwinian perspective.

We review the biology of non-flagellar type-III secretion systems from a Darwinian perspective, highlighting the themes of evolution, conservation, variation and decay. The presence of these systems in environmental organisms such as Myxococcus, Desulfovibrio and Verrucomicrobium hints at roles beyond virulence. We review newly discovered sequence homologies (e.g., YopN/TyeA and SepL). We discuss synapomorphies that might be useful in formulating a taxonomy of type-III secretion. The problem of information overload is likely to be ameliorated by launch of a web site devoted to the comparative biology of type-III secretion ().

Amino Acid Sequence↗
PubMed2003

Myxobacteria: proficient producers of novel natural products with various biological activities--past and future biotechnological aspects with the focus on the genus Sorangium.

Myxobacteria are gram-negative bacteria which are most noted for their ability to form fruiting bodies upon starvation. Within the last two decades, they increasingly gained attention as producers of natural products with biological activity. Here, recent and future biotechnological research on certain key myxobacteria and on their ability to produce natural products is reviewed with the focus on the production of myxovirescin, soraphen and epothilone. Aspects of product improvement and yield as well as statistics regarding secondary metabolite formation are discussed. Future research will deal with the exploitation of the biosynthetic potential of the myxobacteria, for example via the isolation of new myxobacterial species with different physiological properties. Additionally, the genetic potential of myxobacteria to form natural products can be exploited by the identification and activation of biosynthetic gene clusters. These can be found frequently within their genomes, which is shown by the analysis of the unfinished genomes of Myxococcus xanthus and Sorangium cellulosum. The current status of the S. cellulosum functional genome project with model strain So ce56 is discussed.

Biotechnology↗