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At least 307 records · Page 17Linked to original sources
PubMed1979

[Carminomycin induction of single-stranded DNA breaks in Micrococcus luteus cells].

The effect of carminomycin, an amtitumor antibiotic from the anthracycline group on DNA of M. luteus cells was studied. It was shown that carminomycin induced one-thread breaks in DNA. The antibiotic effect was proportional to its concentration and depended on the time of the cell exposure. When the incubation time with carminomycin was longer, there was observed disappearance of a significant part of the breaks. The lower was the antibiotic concentration, the rapider was the process, especially after removal of the antibiotic from the medium. Induction of the one-thread breaks by carminomycin in DNA of the cells of the mutant strain DB-7 of M. luteus was more difficult than in that of the cells of the wild type strain which was indicative of the enzymatic character of most of the breaks and of a special role of UV-endonuclease of M. luteus in this process. On the basis of carminomycin hypersensitivity of the mutant it was concluded that the above enzyme was probably involved in reparation of the DNA damages induced by carminomycin. No two-thread breaks induced by the antibiotic were detected.

Carubicin↗
PubMed1989

Flow microcalorimetric assay of antibiotics--III. Zinc bacitracin and its combinations with polymyxin B sulphate and neomycin sulphate on interaction with Micrococcus luteus.

A flow microcalorimetric assay for zinc bacitracin has been developed which has better reproducibility (relative standard deviation less than 2%) and sensitivity (0.02 micrograms ml-1) than conventional microbiological assays, and requires an assay time of between 7.5-9 h. The assay is not suitable for zinc bacitracin determinations in the presence of equimolar concentrations of polymyxin B sulphate or neomycin sulphate, or of these antibiotics in the proportions in which they occur in the commercial preparation Trisep (ICI, Macclesfield, UK).

Bacitracin↗
PubMed1987

DNA repair by articular chondrocytes. IV. Measurement of Micrococcus luteus endonuclease-sensitive sites by alkaline elution in rabbit articular chondrocytes.

The ability of resting and dividing rabbit articular chondrocytes to repair low doses of ultraviolet (UV) damage was measured through removal of UV endonuclease-sensitive sites (ESS, pyrimidines dimers) as measured by alkaline elution. The repair of damage was significantly (P less than 0.001) greater in dividing than non-dividing cells. An age-related decrease in repair capability was found in resting chondrocytes, but not in their dividing counterpart. These results support earlier findings of unscheduled DNA synthesis by the same cells. (Mech. Ageing Dev., 32: 39-55, 1985).

Animals↗
PubMed1979

Stereochemistry of internucleotide bond formation by polynucleotide phosphorylase from Micrococcus luteus.

Polynucleotide phosphorylase catalyzes the formation of polynucleotides from the Sp diastereomer of adenosine 5'-O-(l-thiodiphosphate) ADPalphaS), whereas the Rp diastereomer is a competitive inhibitor. The absolute configuration of the phosphorothioate diester bond in the polymer was determined by copolymerizing ADPalpha S, Sp isomer with UDP and degrading the resulting copolymer with R Nase A and spleen phosphodiesterase to give, inter alia, uridine 2',-3'-cyclic phosphorothioate. The latter product was shown to be the endo isomer by high-performance liquid chromatography. No evidence for the presence of the exo isomer was obtained. It can thus be concluded that the Sp diastereomer of ADPalphaS polymerizes with inversion of configuration at phosphorus without racemization to give a phosphorothioate diester bond with the Rp configuration.

Kinetics↗
PubMed1981

Stereochemical and kinetic investigation of 32P-labeled inorganic phosphate exchange reaction catalyzed by primer-independent and primer-dependent polynucleotide phosphorylase from Micrococcus luteus.

The SP diastereomer of adenosine 5'-O-(1-thiodiphosphate) (ADP alpha S) is a substrate for the 32P-labeled inorganic phosphate exchange reaction catalyzed by the T and I forms of polynucleotide phosphorylase. The exchange reaction occurs with retention of configuration. This exchange reaction is very slow when only ADP alpha S(SP) is presented but is greatly activated by dinucleotide primers and ADP alpha S(RP), although the latter is not a substrate for the exchange reaction. Ap(S)A(RP) is an approximately 50% better activator of the exchange than the SP diastereomer. Furthermore, high levels of the ADP alpha S(SP) eliminate the activation by primers and by ADP alpha S(RP). A phosphatase activity is present with the I form of the enzyme which converts ADP alpha S(RP) to AMPS. This activity may be responsible for the formation of the 5'-phosphate end group for de novo polymerization or for the processivity of this reaction.

Adenosine Diphosphate↗
PubMed1984

Adaptive response of Micrococcus luteus to alkylating chemicals.

Wild type M. luteus cells have been adapted by a step-wise treatment with sub-lethal concentrations of MNNG. The adapted cells exhibit 5.7 fold increased resistance to the killing effects of the mutagen and a simultaneous efficient removal of various base modifications present in cellular DNA. A protein extract prepared from adapted cells contains inducible repair functions which can reduce 80-90% of the alkylated DNA content of 06-MeG is effected by a transmethylase and there is no concomitant release of the modified base. However, N-3 MeG is released as a free modified base through the action of a DNA glycosylase. The release of N-3 MeA is unaffected by the induction treatment whereas that of N-7 methylpurine is slightly improved in the adapted cells.

Alkylating Agents↗
PubMed1972

Complex lipid requirements for detergent-solubilized phosphoacetylmuramyl-pentapeptide translocase from Micrococcus luteus.

Phospho-MurNAc-pentapeptide translocase activity in the membrane of M. luteus was lost upon addition of the detergent, Triton X-100, but could be restored by addition of lipid fractions to the assay. By assay in the presence of lipid, the activity of the Triton-solubilized enzyme could be measured. The synthesis of C(55)-isoprenyl-P-P-MurNAc-pentapeptide from UDP-MurNAc-pentapeptide required C(55)-isoprenyl-P, and was stimulated by a neutral lipid. The exchange reaction of UDP-MurNAc-pentapeptide with UMP required a polar lipid fraction, but the reaction was not affected by C(55)-isoprenyl-P or the neutral lipid. Thus, measurement of activity of the detergent-solubilized enzyme requires addition of three lipids, the lipid substrate (C(55)-isoprenyl-P), the neutral lipid, and a polar lipid.

Carbon Isotopes↗
PubMed1981

ATP-dependent exonuclease V from Micrococcus luteus. The enzyme-DNA complex, the processive mechanism, and the role of ATP.

Some kinetic predictions of the proposed processive mechanism for the hydrolysis of DNA by the ATP-dependent enzyme exonuclease V have been checked. The method is to trap enzyme molecules not attached to radioactive DNA substrate with an excess of nonradioactive DNA, so that enzyme molecules attached to the radioactive substrate contribute to the liberation of radioactive products only until they dissociate from it. The experiments show that enzyme molecules remain attached to a T7 double-stranded DNA molecule, while hydrolysing it, for about 2 min under our conditions, in agreement with the predictions of the processive mechanism. However, the mechanism of degradation of single-stranded DNA is not processive. Formation of an enzyme-DNA complex is largely dependent on the presence of ATP. This formation does not appear to be synchronous. ATP analogs do not stimulate formation of, nor stabilize, the enzyme-DNA complex. EDTA causes dissociation of enzyme molecules from the DNA complex.

Adenosine Triphosphate↗
PubMed1976

Substrate specificity of the ultraviolet-endonuclease from Micrococcus luteus. Endonucleolytic cleavage of depurinated DNA.

The ultraviolet-endonuclease isolated from Micrococcul luteus, specific for pyrimidine dimers, is able to attack not only ultraviolet-irradiated DNA (leading to 3'OH-5'PO4 single-strand breaks) but also superhelical covalently-closed circular DNA of phage lambda damaged by heating at 70 degrees C, pH 5.93. The number of endonuclease-sensitive defects in the DNA corresponds to the number of alkalilabile bonds (apurinic sites) induced by heating. Competition between ultraviolet-induced lesions and apurinic sites for ultraviolet-endonuclease is demonstrated; the affinity of the enzyme for pyrimidine dimers is about three times that for apurinic sites. Both activities of the ultraviolet-endonuclease are inactivated at 50 degrees C at the same rate. The ultraviolet-endonuclease is able to reduce the infectious activity of depurinated lambda DNA towards Ca2+-treated uvr+ and uvr A Escherichia coli cells. It is concluded that both pyrimidine dimers and apurinic sites can be recognized by one and the same enzyme (the ultraviolet-endonuclease).

Binding, Competitive↗
PubMed1975

Ultraviolet reactivation and ultraviolet mutagenesis of infectious lambda DNA: strong inhibition by treatment of DNA in vitro with UV-endonuclease from Micrococcus luteus.

UV-endonuclease from Microcossuc luteus induces single-stranded breaks in UV-irradiated DNA of phage lambda and the average length of the fragments produced (after UV-doses to DNA of 135 and 675 erg/mm2) is equal to the average spacing between pyrimidine dimers. The plaque-forming ability of UV-irradiated lambda DNA used to infect Ca++-treated uvr A6, uvrB5 or uvrC34 recipient Escherichia coli cells (but not uve+ cells) may be significantly enhanced by treatment of lambda DNA with UV-endonuclease. This enzyme strongly decreases the reactivation of UV-irradiated lambda DNA caused by UV-irradiation of uvr+ or uvrA6 Ca++-treated cells and eliminates most clear-mutations especially if mutations are analysed using Ca++-treated uvr A6 recipient cells. It is concluded that UV-endonuclease switches a significant part of potentially mutagenic pyrimidine dimers from the UV-induced "error-prone" repair pathway to "error-free" excision repair pathway.

Centrifugation, Zonal↗
PubMed1987

The roles of different excision-repair mechanisms in the resistance of Micrococcus luteus to UV and chemical mutagens.

M. luteus mutants showing increased sensitivity to both UV and 4-NQO were isolated after the treatment of parental ATCC4698 strain with MNNG. The mutants were also highly sensitive to mitomycin C, cis-platinum, 8-methoxypsoralen (8-MOP) plus near-UV and angelicin plus near-UV in various degrees. The endonuclease activity specific for pyrimidine dimers in UV-irradiated DNA was normally detected in extract of the mutants. With regard to host-cell reactivation ability the mutants fell into two groups. The hcr- mutants lacked the ability to reactivate UV-damaged N6 phage and were resistant to X-rays. The incision of DNA did not occur during incubation after the treatment with angelicin plus near-UV in the hcr- mutants, whereas it occurred in the parental strain. The facts indicate that the hcr- mutants are defective in the incision mechanism which has a wide substrate specificity, similar to the UVRABC nuclease of E. coli. On the other hand, the incision of DNA and the removal of UV-induced thymine dimers from DNA occurred in the hcr- mutants as well as in the parental strain, which is ascribed to the UV endonuclease activity. Compared with the hcr- mutants, hcr+ mutants were highly sensitive to X-rays, like recA- mutants of E. coli.

4-Nitroquinoline-1-oxide↗
PubMed1977

Endonuclease activities in extracts of Micrococcus luteus that act on gemma-irradiated DNA.

Several protein fractions containing endonuclease activity against gemma-irradiated DNA (gamma-endonuclease) were isolated from M. luteus. The crude extract was eluted on a phosphocellulose column and chromatographed on TEAE cellulose and subsequently on hydroxyapatite. Five peaks of gamma-endonuclease were obtained from each preparation. Repeated experiments showed comparable chromatographic behavior of the fractions. There was no detectable activity of U.V.-endonuclease in the fractions with gamma-endonuclease but a small contamination of endonuclease against unirradiated DNA and against DNA with apurinic sites. The gamma-endonuclease is stimulated by, but is not dependent on, magnesium. Several tests for endonuclease activity have been used: the analysis of strand breaks in calf-thymus DNA or in PM2 DNA, and the determination of end-groups formed by endonuclease, either 3'OH end-groups or phosphomonoester end groups. From the results obtained it can be assumed that the strand breaks induced by the gamma-endonuclease carry 3'OH and 5' phosphate end groups.

Cobalt Radioisotopes↗