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PubMed1983

The myxopyronins, new inhibitors of bacterial RNA synthesis from Myxococcus fulvus (Myxobacterales).

From the culture supernatant of the myxobacterium, Myxococcus fulvus strain Mx f50, an antibiotic activity was isolated which blocked growth of many Gram-positive and several Gram-negative bacteria, but not of yeasts and fungi. The activity consisted of two closely related compounds, myxopyronins A and B. The myxopyronins appear to be new antibiotics, and seem to specifically inhibit bacterial RNA polymerase.

Animals↗
PubMed1983

The myxovalargins, new peptide antibiotics from Myxococcus fulvus (Myxobacterales). I. Cultivation, isolation, and some chemical and biological properties.

Antibiotic activity was isolated from the culture supernatant of the myxobacterium Myxococcus fulvus strain Mx f65. It was active against Gram-positive bacteria (MIC 0.3 approximately 5 micrograms/ml), at higher concentrations also against Gram-negative ones (MIC 6 approximately 100 micrograms/ml), and not at all against yeasts and molds. The activity could be resolved into 4 closely related peptides, the myxovalargins. One of them, myxovalargin A, was by far the most plentiful. The compounds appear to be new antibiotics and seem to interfere with protein synthesis.

Anti-Bacterial Agents↗
PubMed1984

A macrocyclic antibiotic M-230B produced by Myxococcus xanthus. Isolation and characterization.

Myxococcus xanthus strain M516E produced at least three related antibiotics against Gram-positive and Gram-negative bacteria. From physico-chemical properties, a main component was identical to myxovirescin A and a second component, designated M-230B was found to be an antibiotic which is closely related to myxovirescin A. The structure of M-230B was determined from its physico-chemical properties, especially from 13C NMR spectrum as compared with that of myxovirescin A. The addition of alcohol, such as isobutyl alcohol, to the culture medium markedly stimulated production of the antibiotics.

Alcohols↗
PubMed1979

Two methods of large-scale extraction of an antibiotic produced by Myxococcus coralloides.

Two methods for the isolation of an antibiotic produced by Myxococcus coralloides have been developed: the chloroform extraction method and the charcoal adsorption method. The recovery of antibiotic in each case was 25% and 30%, respectively, by the two methods. Although the two methods yield a relative low recovery, the charcoal adsorption method seems more attractive and promising due to its simplicity and economic advantages.

Adsorption↗
PubMed1979

Biological activity of an antibiotic produced by Myxococcus coralloides.

A strain of Myxococcus coralloides was isolated which produced an antibiotic active against Gram-positive bacteria and also against Neisseria sp at high levels of antibiotic. The antibiotic was bactericidal on sensitive growing bacteria. It was inactive on non-growing cells and also on cells whose growth has been stopped by addition of chloramphenicol. Strains of S. aureus resistant to several antibiotics, including penicillin and ampicillin, were also sensitive to this antibiotic.

Anti-Bacterial Agents↗
PubMed1990

Nucleoside diphosphate kinase from Myxococcus xanthus. I. Cloning and sequencing of the gene.

By photoaffinity labeling with a photolysable analog of GTP, 8-N3GTP, we were able to find at least five distinct GTP-binding proteins in Myxococcus xanthus; two of them located in the membrane and the other three in the soluble fraction. The amino-terminal sequence of the 16-kDa GTP-binding protein from the soluble fraction was determined, and the gene that encodes this protein was isolated and cloned using degenerate oligonucleotides as a probe. The DNA sequence of the gene was determined, which did not show similarity with other known proteins. The gene product was overexpressed in Escherichia coli, by using the lacZ promoter, to a level of 13% of the soluble protein. Attempts to isolate deletion mutants were unsuccessful, although double crossing-over events leading to a deletion mutation of the gene were detected by Southern blot hybridization. This result indicates that this gene is essential for cell growth. In the following paper (Muñoz-Dorado, J., Inouye, S., and Inouye, M. (1990) J. Biol. Chem. 265, 2707-2712), the gene product was biochemically characterized and identified to be a nucleoside diphosphate kinase.

Affinity Labels↗
PubMed1990

Nucleoside diphosphate kinase from Myxococcus xanthus. II. Biochemical characterization.

The gene that encodes the 16-kDa GTP-binding protein from Myxococcus xanthus has been cloned, and its DNA sequence has been determined. The gene has been expressed in Escherichia coli by using the lacZ promoter, and its gene product was overproduced (Muñoz-Dorado, J., Inouye, M., and Inouye, S. (1990) J. Biol. Chem. 265, 2702-2706). The gene product thus overproduced in E. coli was purified to homogeneity by a simple four-step procedure and crystallized. Gel filtration of the purified protein revealed that the protein forms a complex of an apparent molecular weight of 50,000, indicating that it exists as a trimer in the cell. It was found that the purified protein can bind not only GTP, but also equally well the other nucleoside diphosphates and triphosphates with no specificity for either the base or the sugar. Nucleoside monophosphates, Pi, and pyrophosphate do not bind to the protein. In the presence of Mg2+, the protein hydrolyzes nucleoside triphosphates to diphosphates and Pi. However, in the presence of EDTA, most of the phosphate remains bound to the protein. The phosphorylated protein can then transfer the phosphate group to a nucleoside diphosphate to form the corresponding nucleoside triphosphate in the presence of Mg2+. The reaction is reversible, and it is considered to occur by a two-step ping-pong mechanism. These results unambiguously demonstrate that the M. xanthus 16-kDa GTP-binding protein is a nucleoside diphosphate kinase.

Adenosine Triphosphate↗
PubMed1988

A new species of multicopy single-stranded DNA from Myxococcus xanthus with conserved structural features.

Myxobacteria have been shown to contain a large number of branched RNA-linked single-stranded DNA (multicopy single-stranded DNA (msDNA] molecules. In addition, we found that Myxococcus xanthus contains another smaller msDNA-like molecule, designated mrDNA, consisting of a 65-base single-stranded DNA covalently linked by a 2',5'-phosphodiester linkage to a 49-base branched RNA. In spite of their different primary sequences, the RNA-linked mrDNA is remarkably similar in secondary structure to msDNA, sharing similar stem-loop folding as well as the unique 2',5'-phosphodiester linkage. These results indicate that these novel molecules are synthesized by common molecular mechanisms.

Base Sequence↗
PubMed1989

Structural requirements of the RNA precursor for the biosynthesis of the branched RNA-linked multicopy single-stranded DNA of Myxococcus xanthus.

A precursor RNA molecule (pre-msdRNA) of approximately 375 bases is considered to form a stable secondary structure which serves as a primer as well as a template to synthesize the branched RNA-linked multicopy single-stranded DNA (msDNA) of Myxococcus xanthus. When 3-base mismatches were introduced into the stem structure immediately upstream of the branched rG residue to which msDNA is linked by a 2',5'-phosphodiester linkage, the production of msDNA was almost completely blocked. However, if additional 3-base substitutions were made on the other strand to resume the complementary base pairing, msDNA production was restored, being consistent with the proposed model of msDNA synthesis. We also found that the branched rG residue of pre-msdRNA could not be replaced with either rC or rA, while the 5' end (dC) of msDNA which is linked to the branched rG could be substituted with a dG residue. Together with several other mutations, the structural requirements of pre-msdRNA are discussed with respect to the mechanism of msDNA biosynthesis.

DNA, Bacterial↗
PubMed1989

Myxococcus xanthus msDNA.Mx162 exists as a complex with proteins.

Myxococcus xanthus, a myxobacterium, contains a peculiar branched RNA-linked DNA called msDNA. Reverse transcriptase has been shown to be required for the production of msDNA. Existence of proteins that bind to one of the two msDNAs in M. xanthus, msDNA.Mx162, was examined by gel retardation assays. Total cell-free extract yielded two distinct retarded bands. Both bands were sensitive to treatment with proteinase K, indicating that there is a protein(s) that is able to bind to msDNA. Further, the formation of the bands was inhibited by the addition of nonradioactive msDNA but not by a large excess of poly(dA) in the presence of a 5000-fold excess of poly(dI.dC).poly(dI.dC). In vivo footprinting using dimethyl sulfate revealed that the deoxynucleotide stretch from 60 to 161 is protected. When a M. xanthus cell lysate was centrifuged in a 16-30% glycerol gradient, msDNA was found to sediment in two peaks: a major peak corresponding in size to 14 S, and a minor one at 5 S. These results indicate that msDNA.Mx162 exists as a complex with specific proteins in the cell.

Base Sequence↗
PubMed1987

Induction, purification and some properties of phage tail-like particles from Myxococcus coralloides D.

Myxococcus coralloides D was lysogenic for a defective prophage. The particles of the defective bacteriophage could be induced by ultraviolet light and mitomycin C, but the particles did not appear in the supernatants, unless the cells were lysed with chloroform. The phage tails were purified by using a two-phase separation method, ultracentrifugation, chromatography through Sepharose 4B, treatment with chloroform, dialysis and centrifugation on a sucrose gradient. The chemical analysis of the purified samples revealed that the phage tails contained only proteins, neither DNA nor RNA. The different parts of the phage tails (sheath, core and baseplate) did not have the same sensitivity to the chemical and physical agents which were assayed.

Bacteriophages↗
PubMed1988

Characterization of calcium-binding sites in development-specific protein S of Myxococcus xanthus using site-specific mutagenesis.

Protein S, the most abundant protein synthesized during development of the Gram-negative bacterium Myxococcus xanthus, assembles on the surface of the spores. It can be dissociated from the spores using divalent metal chelators and will reassemble on the spores in the presence of calcium. The amino acid sequence of protein S contains regions which have homology to the calcium-binding sites of calmodulin. Protein S was found to bind 2 mol of calcium/mol of protein with Kd values of 27 and 76 microM. Using oligonucleotide-directed site-specific mutagenesis, the gene coding for protein S was changed in each of two regions of homology to calmodulin (Ser40----Arg,Ser129----Arg), and a double mutant was also constructed. Each mutant gene was then transduced into the genome of a M. xanthus strain from which the wild-type genes had been deleted. All three mutants produced protein S normally during development. One of the mutants (Ser129----Arg) had normal amounts of protein S on its spores, whereas the other (Ser40----Arg) bound much less and the double mutant had virtually none. Analysis of the calcium binding affinities of the purified proteins showed that [Arg40]protein S and [Arg40, Arg129]protein S did not bind detectable quantities of calcium, whereas [Arg129]protein S bound less calcium than the wild-type protein and with a reduced affinity.

Amino Acid Sequence↗
PubMed1983

Tandem repeat of the genes for protein S, a development-specific protein of Myxococcus xanthus.

Protein S, a development-specific protein of Myxococcus xanthus is produced only during fruiting body formation. More than 15% of total protein synthesis during this period is accounted for by the production of protein S. The genes for protein S were identified and cloned with the use of mixed probes consisting of eight synthetic oligodeoxyribonucleotides (tetradecamers) which correspond to a carboxyl-terminal portion of protein S. The two genes are oriented in the same direction and are separated approximately 1.2 kilobases. The DNA sequences of the carboxyl-terminal portions of the two genes reveal that both can code for the identical eleven amino acid sequence which corresponds to the carboxyl-terminal end of protein S. However, there are a few base substitutions upstream of these regions. This duplication of genes in M. xanthus may facilitate the extremely rapid synthesis of protein S during fruiting body formation.

Bacteria↗
PubMed1983

Pigments with antibiotic activity from Myxococcus coralloides.

A strain of Myxococcus coralloides produces pigments with antibiotic activity. The pigments are non-diffusible and become detectable at the beginning of the autolytic phase. Red pigments produced by vegetatively growing cells were extracted by acetone treatment. The crude extract when chromatographed yielded several fractions, two of which were active against certain Gram-positive bacteria. Both fractions were partial purified in thin layer chromatography and can be differentiated according to colour, polarity and absorption spectrum. Production of active pigments is increased by nicotine and inhibited by diphenylamine. The pigments are also compared with the antibiotic produced by this bacterium.

Anti-Bacterial Agents↗
PubMed1984

Verification of protein sequence by fast atom bombardment mass spectrometry. Amino acid sequence of protein S, a development-specific protein of Myxococcus xanthus.

A mass spectrometric method was applied to protein S, a development-specific protein of Myxococcus xanthus, in order to verify the amino acid sequence deduced from the nucleotide sequence of its gene. On examining proteolytic digests of the protein by fast atom bombardment mass spectrometry without separation of individual peptides, signals corresponding to individual peptides were observed in the mass spectra. The mass values of the observed signals were correlated to the theoretical mass values calculated from the predicted amino acid sequence, thereby identifying the peptides and proving the accuracy of the sequence. The previous finding that protein S is the product of the second gene of the two tandemly repeated genes on the M. xanthus chromosome ( Inouye , S., Franceschini , T., and Inouye , M. (1983) Proc. Natl. Acad. Sci. U.S.A. 80, 6829-6833) is now unambiguously confirmed.

Amino Acid Sequence↗
PubMed1980

Preliminary crystallographic data for protein S, a development-specific protein of Myxococcus xanthus.

Protein S, which is produced only during the developmental cycle of Myxococcus xanthus, has been crystallized using 2-methyl-2,4-pentanediol as a precipitating agent. The crystals were very stable in the x-ray beam for up to 150 h and diffracted to a resolution of 2.2 A. The crystals belong to the orthorhombic space group P212121 with unit cell dimensions a = 52.99 A, b = 60.10 A, and c = 102.16 A. Each asymmetric unit consists of two monomers of Protein S, each having a molecular weight of 23,000.

Bacterial Proteins↗
PubMed1981

Purification and characterization of myxobacterial hemagglutinin, a development-specific lectin of Myxococcus xanthus.

Myxococcus xanthus is a Gram-negative bacterium that has a complex life cycle which includes cellular aggregation and sporulation. During the period of cellular aggregation, a lectin-like protein called myxobacterial hemagglutinin (MBHA) is synthesized. A four-step purification procedure for MBHA is described. It consists of chromatography on DEAE-cellulose, CM-cellulose, and hydroxyapatite, followed by gel filtration on Bio-Gel P-30. This procedure gives good yields of MBHA (40-50%) free of contaminating proteins. The purified protein has been partially characterized. It exists as a monomer in solution with an apparent Mr = 28,000 and an isoelectric point of 8.3. The amino acid composition of MBHA has been determined. It shows a very high content of glycine (19%) as well as aromatic amino acids (9%); it has a low percentage of charged amino acids. No detectable carbohydrate was found in a large sample (50 micrograms) of MBHA. The far-ultraviolet CD spectrum of MBHA indicates a secondary structure which contains very little alpha-helix, 50 +/- 10% beta-sheet, and 50 +/- 10% random coil. MBHA comprises 1-2% of soluble protein of M. xanthus at the time of cellular aggregation. The fact that it is a lectin suggests that it may play a role in cell-cell recognition or adhesion.

Amino Acids↗
PubMed1981

Localization of myxobacterial hemagglutinin in the periplasmic space and on the cell surface of Myxococcus xanthus during developmental aggregation.

During the period of developmental aggregation which precedes fruiting body formation, the bacterium Myxococcus xanthus produces a large amount of a lectin called myxobacterial hemagglutinin (MBHA). Sequential cell washing, osmotic shock, and disruption of developmental cells showed that as much as 90% of the total hemagglutinating activity can be recovered in the wash and shock fractions. Analysis of the wash and shock fluids by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that these fractions are enriched in MBHA. MBHA was detected on the surface of developmental cells but not vegetative cells by immunofluorescent staining procedures. The fluorescence was localized in distinct patches which were usually located at one or both of the cell poles, although patches of fluorescence could also be seen at additional sites as well. The presence of MBHA on the cell surface was also detected by electron microscopy of developmental cells stained with ferritin-conjugated antibody. Most of the cells showed distinct patches of ferritin staining at one or both of the cell poles; nonpolar staining, which was also observed, was always accompanied by membrane protuberances. The amino acid sequence of the NH2 terminus of MBHA was determined and found to be extremely hydrophobic, suggesting that it may function as a nonprocessed signal for transmembrane transport. The site-specific localization of MBHA at the cell poles suggests that it may function in end-to-end cellular interactions during aggregation.

Amino Acid Sequence↗