UV Survival of Human Mycoplasmas: Evidence of Dark Reactivation in <i>Mycoplasma buccale</i>

Aoki, Shigeji; Ito, Shun; Watanabe, Takehiko

doi:10.1111/j.1348-0421.1979.tb00451.x

Cited by 20 publications

(9 citation statements)

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“…It has been suggested that variations in the amounts and/or activities of enzymes involved with DNA repair could cause the biased mutation pressure in these organisms (33,47). However, there have been few studies on DNA repair processes and the enzymes involved with such processes in these organisms (1,12,18).…”

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confidence: 99%

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A mollicute (mycoplasma) DNA repair enzyme: purification and characterization of uracil-DNA glycosylase

Williams

Pollack

1990

J Bacteriol

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The DNA repair enzyme uracil-DNA glycosylase from Mycoplasma lactucae (831-C4) was purified 1,657-fold by using affinity chromatography and chromatofocusing techniques. The only substrate for the enzyme was DNA that contained uracil residues, and the Km of the enzyme was 1.05 + 0.12 FM for dUMP containing DNA. The product of the reaction was uracil, and it acted as a noncompetitive inhibitor of the uracil-DNA glycosylase with a Ki of 5.2 mM. The activity of the enzyme was insensitive to Mg2+, Mn2 , Zn2+, Ca2 , and Co2+ over the concentration range tested, and the activity was not inhibited by EDTA. The enzyme activity exhibited a biphasic response to monovalent cations and to polyamines. The enzyme had a pI of 6.4 and existed as a nonspherical monomeric protein with a molecular weight of 28,500 ± 1,200. The uracil-DNA glycosylase from M. lactucae was inhibited by the uracil-DNA glycosylase inhibitor from bacteriophage PBS-2, but the amount of inhibitor required for 50% inhibition of the mycoplasmal enzyme was 2.2 and 8 times greater than that required to cause 50% inhibition of the uracil-DNA glycosylases from Escherichia coli and Bacillus subtlis, respectively. Previous studies have reported that some mollicutes lack uracil-DNA glycosylase activity, and the results of this study demonstrate that the uracil-DNA glycosylase from M. lactucae has a higher Km for uracil-containing DNA than those of the glycosylases of other procaryotic organisms. Thus, the low G+C content of the DNA from some molicutes and the A * T-biased mutation pressure observed in these organisms may be related to their decreased capacity to remove uracil residues from DNA.

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confidence: 99%

“…Inhibitor activity was determined in both a HEPES (N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid)-buffered system (HEP) and a Tris-buffered system (TRI). The HEP system contained the following in a total volume of 0.2 ml: 70 mM HEPES-KOH (pH 7.8), 1 (Fig. 1B) ULT uracil residues ( Fig.…”

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confidence: 99%

A mollicute (mycoplasma) DNA repair enzyme: purification and characterization of uracil-DNA glycosylase

Williams

Pollack

1990

J Bacteriol

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“…laidlawii (Ghosh et al, 1978). It should be noted that Aoki et al (1979) were unable to detect a dark repair system in M. buccale and Ghosh et al (1977) failed to observe both photoreactivation and dark repair in M. gallisepticum. This last point raises questions about how an organism that appears to lack these critical repair systems is able to maintain fidelity in the replication of its genome.…”

Section: Dna Repair and Recombinationmentioning

confidence: 89%

“…Survival curves versus UV exposure typically show a shoulder near the origin followed by logarithmic killing (Aoki et al, 1979;Maniloff and Morowitz, 1972). Dark repair and photoreactivation have been demonstrated in A. laidlawii (Das et al, 1972).…”

Section: Dna Repair and Recombinationmentioning

confidence: 99%

Development of molecular genetic approaches to study mycoplasma pathogenesis

Mahairas

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Rogers et al., 1985;Woese, 1985). Rifampin sensitivity, a general property of eubacterial DNA-dependent RNA polymerases (Sippel and Hartman, 1968), also provided supportive evidence of the 3 phylogenetic relationships. Rifampin acts on the P subunit of the RNA polymerase holoenzyme to inhibit the initiation step of transcription (Rabussay and Zillig, 1969). Gadeau et al. (1986) show that the growth of five representative Mollicutes was insensitive to rifampin in contrast to E. coli which was fully inhibited. Additional evidence was provided by in vitro experiments that showed that S. apis and S. melliferim enzymes were rifampin resistant even though their subunit structure strongly resembled that of E. coli (Gadeau et al., 1986).Interestingly, the RNA polymerase of A. laidlawii showed a marked sensitivity to rifampin as compared with the Spiroplasma enzymes but there was a greater degree of resistance than with the E. coli enzyme (Gadeau et al., 1986). Therefore it is believed that the sensitivity to rifampin was lost during the splitting of the Acholeplasma branch of the phylogenetic tree.The Mycoplasma GenomeThe tRNA species. The M. capricolum genome also contained two sets of rRNA genes compared to the ten sets of Bacillus subtilis (Widom et al., 1988).All species of the Mollicutes have a relatively low G + C content although a large variation exists (Razin and Freundt, 1984). The G + C content of all species of Ureaplasma was reported to be about 28% while that of most organisms in the genus Mycoplasma was between 24-30% (Razin and Freundt, 1984). It should be noted that the G + C content of M.gallisepticum was 32% while that of M. pneumoniae was about 38% (Razin and Freundt, 1984). These organisms are the prototypes of a small group of higher G + C mycoplasmas (Razin and Freundt, 1984). Halden et al., 1989). iSc/Nl is an isoschizomer of Hhal that recognizes the sequence 5'-GCGC-3' (Stephens, 1982) cleaving between the first G and C generating a two base 5' , 1985).A system to generate energy from ATP is also required for autonomous growth.Schiefer and Schummer (1982) examined several mycoplasmas and found that energy is generated by a membrane bound proton-translocating adenosine triphosphatase that hydrolyzes ATP formed in glycolysis leading to proton extrusion. Additionally, Zilberstein et al. (1986) showed that the FIFQ ATPase of several mycoplasmas were immunologically crossreactive with that of E. coli in the active site region but differed in that the mycoplasma enzymes had an altered structure and were covalently anchored to the membrane. About 270 genes in the E.coli genome encode components of the protein and nucleic acid synthesizing machinery, including RNA and DNA polymerases, ribosomal proteins, tRNAs and additional transcription and translation factors (Muto, 1987). Thus it is thought that in the mycoplasmas, a major portion of the coding regions is devoted to these essential functions as well as the generation of energy making the mycoplasmas the minimal information coding for a livi...

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“…The mycoplasmas arc exceedingly sensitive to ultraviolet (UV) and gamma radiation . Survival curves versus UV exposure typically show a shoulder near the origin followed by logarithmic killing (Aoki et al, 1979;Maniloff and Morowitz, 1972). Dark repair and photoreactivation have been demonstrated in A. laidlawii (Das et al, 1972).…”

Section: Dna Repair and Recombinationmentioning

confidence: 99%

Development of molecular genetic approaches to study mycoplasma pathogenesis

Mahairas

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UV Survival of Human Mycoplasmas: Evidence of Dark Reactivation in Mycoplasma buccale

Cited by 20 publications

References 37 publications

A mollicute (mycoplasma) DNA repair enzyme: purification and characterization of uracil-DNA glycosylase

A mollicute (mycoplasma) DNA repair enzyme: purification and characterization of uracil-DNA glycosylase

Development of molecular genetic approaches to study mycoplasma pathogenesis

Development of molecular genetic approaches to study mycoplasma pathogenesis

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