Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mycoplasma pulmonis has substantial DNase activity exposed on the cell surface. At least part of this activity is attributable to an endonuclease. The activity is destroyed at 56 degrees C and inhibited by either 5 mM EDTA or 10 mM zinc chloride. It can also be eliminated by treatment of intact organisms with trypsin and is regenerated by incubation of the treated organisms in a medium that supports protein synthesis. DNase exposed at the cell surface constitutes 20% of the total DNase activity present in M. pulmonis extracts.
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PMID:Identification and preliminary characterization of external membrane-bound nuclease activities in Mycoplasma pulmonis. 394 Oct 2

The age and time of year when colonisation of the nasal cavity of lambs by Mycoplasma ovipneumoniae occurs; the persistence of the organism, and its prevalence in the lungs at slaughter were examined in 2 flocks of sheep in New Zealand. No colonisation had occurred at the time of weaning at 6-7 weeks, but M. ovipneumoniae was recovered from most lambs on at least one occasion before they were slaughtered when about 8 months old. In most cases, colonisation of the nasal cavity by M. ovipneumoniae was a transient phenomenon. At slaughter M. ovipneumoniae was recovered from the lungs of 89% of the lambs of one flock and 80% of the other flock. Bacterial restriction endonuclease DNA analysis (BRENDA) of 34 nasal isolates from one flock showed that it was possible to identify 7 "groups" each with markedly different BRENDA patterns. Lambs initially colonised by one strain, often lost that strain, and if recolonisation occurred it was with a different strain. M. ovipneumoniae was recovered at slaughter from the lungs of most lambs, both normal and pneumonic. The isolates from one flock were examined by BRENDA, and approximately 90% of them gave similar or identical patterns. The predominant strain isolated from the lungs had been recovered from the nasal cavity of many of the lambs about 3 weeks earlier. This suggests that the nasal and lung isolates do not represent independent populations. However, nasal strains may differ in their ability to colonise the lungs.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Colonisation of the respiratory tract of lambs by strains of Mycoplasma ovipneumoniae. 409 99

The small size of the mollicute genome considerably restricts the amount of genetic information available to the organisms. This is reflected in the relatively small number of cell proteins synthesized, the lack of many biosynthetic pathways and the marked dependence on exogenous nutrients for growth. The protein synthesizing machinery of mollicutes resembles that of eubacteria and is sensitive to the same antibiotics, except for rifampicin, to which RNA polymerases of mollicutes appear resistant. The mollicute ribosomes are built of 50 S and 30 S subunits and contain about 50 different proteins and 5 S, 16 S and 23 S rRNA, as in eubacteria. However, the 5 S rRNA in mollicutes appears shorter (107-112 nucleotides) than in eubacteria (116-120 nucleotides). We hybridized restriction endonuclease-digested DNA from a variety of Mycoplasma, Ureaplasma, Acholeplasma and Spiroplasma species with nick-translated probes consisting of defined portions of the rrnB rRNA operon of Escherichia coli and the rRNA operon of M. capricolum. The results suggest the presence of only one or two sets (operons) of rRNA genes in the genome of Mollicutes, a number falling considerably below that of the eubacteria examined so far but resembling that found in archaebacteria. Our data also indicate a marked nucleotide sequence homology along the rrnB rRNA operon of E. coli and the rRNA operons of the various mollicutes, indicating that the rRNA genes in mollicutes are linked in the classical prokaryotic fashion 16 S-23 S-5 S. Each mollicute appeared to possess, on its genome, different flanking sequences adjacent to the rRNA operon(s), resulting in species-specific hybridization patterns.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Molecular and biological features of mollicutes (mycoplasmas). 620 Oct 98

DNA segments carrying rRNA genes of Mycoplasma capricolum have been cloned and characterized by restriction endonuclease mapping, DNA-RNA hybridization and nucleotide sequencing. The M. capricolum genome has two sets of rRNA gene clusters, where the arrangement is in the order of (5')16S-23S-5S(3'). The spacer region between 16S and 23S rDNA is extremely rich in AT and does not carry any tRNA genes.
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PMID:Organization of ribosomal RNA genes in Mycoplasma capricolum. 620 57

Previous investigation of the ability of cytomegalovirus and varicella-zoster virus to replicate in a variety of cell lines suggested that both virus types plaqued with high efficiency in mink lung cells. However, many of the virus isolates used appeared to be contaminated with mycoplasma. We now report that the observed cytopathic effect is due to a mycoplasma which grows lytically to high titre in mink lung cells, but is difficult to cultivate in cell-free media. The mycoplasma was plaque-purified and shown to contain DNA with a buoyant density of 1.684 g/ml, with restriction endonuclease patterns identical to the porcine mycoplasma M. hyorhinis. This was confirmed by serological identification.
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PMID:The plaque-forming factor for mink lung cells present in cytomegalovirus and herpes-zoster virus stocks identified as Mycoplasma hyorhinis. 627 3

A library of cloned Mycoplasma hyorhinis genomic sequences was constructed by incorporation of EcoRI digestion fragments of mycoplasma DNA into the lambda Charon 4A bacteriophage vector. Immunological screening of recombinant phage plaques identified clones containing genes encoding mycoplasma antigenic structures expressed in an Escherichia coli host. Two such recombinant phage isolates, lambda Ch4A-MhrG1 and lambda Ch4A-MhrG28, were defined and found to contain distinct genomic sequences by analysis of restriction endonuclease fragments. Inoculation of mice with recombinant gene products from lambda Ch4A-MhrG1 yielded antiserum selectively recognizing a Mr 29,500 trypsin-sensitive mycoplasma constituent. This established a means for producing selected immunogenic mycoplasma component in a bacterial host. The cloned genomic sequences of M. hyorhinis encoding expressed mycoplasma antigens represent molecular probes that can be characterized both by specific DNA sequences and by the antigenic structure of corresponding gene products. These genomic fragments define initial physical markers of the M. hyorhinis genome and may be useful in assessing antigenic and molecular genetic relationships within the genus Mycoplasma and among other members of the class Mollicutes.
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PMID:Cloned genomic DNA sequences from Mycoplasma hyorhinis encoding antigens expressed in Escherichia coli. 634 24

The number and organization of ribosomal RNA (rRNA) genes in the genome of Mycoplasma, Ureaplasma, Acholeplasma and Spiroplasma species were studied by the Southern hybridization technique. Restriction endonuclease-digested DNAs of the organisms were hybridized with nick-translated probes consisting of defined portions of the rrnB rRNA operon of Escherichia coli and with a recombinant plasmid pMC5 constructed of pBR325 and an insert containing M. capricolum genes for 23S, 5S and most of the 16S rRNA gene. The hybridization data indicate the presence of only one or two sets of rRNA genes in the mollicutes tested, a number lower than in eubacteria. The rRNA genes in mollicutes appear to be organized as clusters (acting apparently as operons) in the typical prokaryotic fashion, 5'-16S-23S-5S-3'. Despite the marked sequence homology shared by the rRNA operons of the different mollicutes and of E. coli, the operons are not identical. Thus, there is an EcoRI restriction site in the 16S rRNA genes in only 8 of the 13 species tested. The recombinant plasmid pMC5 has provided a sensitive probe for detection and identification of mollicutes in contaminated cell cultures. The purified DNA of the tested cell culture, or its supernatant fluid, was digested by EcoRI, and Southern blot hybridization of the products was performed with nick-translated pMC5. The probe did not hybridize with eukaryotic DNA. Each of the mollicutes species examinated exhibited a species-specific hybridization pattern. The hybridization tests enabled the identification of the four most prevalent mycoplasma contaminants of cell cultures, M. orale, M. hyorhinis, M. arginini and A. laidlawii. The test is capable of detecting 1 ng of mycoplasmal DNA, roughly equivalent to the DNA content of 10(5) mycoplasmas. The possibility of using this approach for detection and identification of noncultivable mycoplasmas in plant and insect tissues is under investigation.
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PMID:Mycoplasmal ribosomal RNA genes and their use as probes for detection and identification of Mollicutes. 651 51

Extracts of the Mollicutes Acholeplasma equifetale, Acholeplasma laidlawii B, Mycoplasma arthritidis. Mycoplasma pulmonis, and Mycoplasma pneumoniae had DNase and endonuclease activity. A. laidlawii B had at least two peaks of DNase activity in sucrose gradients with sedimentation coefficients of 3.1S and 4.3S. These fractions also had endonuclease activity with different substrate specificities. A. laidlawii B may have more than two peaks of endonuclease activity in sucrose gradients.
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PMID:Properties of the nucleases of mollicutes. 681 65

Mycoplasmal contamination of HIV-1-infected cells has been found to induce reduction of reverse transcriptase (RT) activity; however, the exact mechanism of this phenomenon was not clearly elucidated. Our results indicate that the apparent reduction in RT activity is due to a calcium-dependent nuclease(s) that is (are) produced by contaminating mycoplasmas. The interference with the RT assay was found to be due to the degradation of products of the RT activity. Addition of EGTA at a 1 mM concentration was sufficient to remove the inhibitory effect. The particular HIV-1-producing cell line that was under study was found to be contaminated with Mycoplasma fermentans and Mycoplasma pirum and the latter was isolated in pure culture. Nuclease activity was also observed with pure cultures of mycoplasmas from different species. The activity was found to be of the endonuclease type because it was active with both supercoiled and linear DNAs.
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PMID:Inhibition of HIV type 1 reverse transcriptase assay by nucleases produced by contaminating mycoplasmas. 753 61

ICR mice were infected intranasally with Mycoplasma pulmonis isolated freshly from the lungs of a rat with pneumonia. We demonstrated with high reproducibility the expressions of messenger RNAs of cytokines, tumor necrosis factor alpha (TNF alpha) and interferon gamma (IFN gamma) in the lung tissue of M. pulmonis-infected mice by the reverse transcriptase-polymerase chain reaction and confirmed specific mRNA of the cytokines by restriction endonuclease digestion. Both the viable population of M. pulmonis in the lung tissue and the titers of the neutralizing antibody in the serum increased between 7 and 21 days, and reached their maximum 35 days after infection. The pneumonia in mice progresses with the development of lung lesions after 7 days of infection. The early lesions are characterized primarily by neutrophils and edema in the alveolar spaces. mRNAs prepared from the lung tissue of M. pulmonis-infected and -uninfected mice were also tested for the presence of messages specific to TNF alpha and IFN gamma by the reverse transcriptase-polymerase chain reaction. The expression of the genes encoding TNF alpha and IFN gamma was constitutively demonstrated from 24 hr through 35 days after the intranasal inoculation of M. pulmonis. Furthermore, cells of two types, adherent and nonadherent cells, in bronchoalveolar lavage fluids obtained from the mice 3 weeks after inoculation of M. pulmonis were also found to express the genes of TNF alpha and IFN gamma respectively. These data suggest that these cytokines would play a role in both stimulation in the development of pathological changes in mycoplasmal infection, affecting the inflammatory responses.
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PMID:Gene expression of tumor necrosis factor alpha and interferon gamma in the lungs of Mycoplasma pulmonis-infected mice. 793 58


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