• Journal of Microbiology
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• v.38 no.1
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• pp.18-23
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• 2000

Streptomyces coelicolor produces three kinds of catalases to cope with oxidative stress and to allow normal differentiation. Catalase A is the major vegetative catalase which functions in removing hydrogen peroxide generated during the process of aerobic metabolism. To understand the regulatory mechanism of response against oxidative stress, hydrogen peroxide-resistant mutant (HR4O) was isolated from S. coelicolor J1501 following UV mutagenesis. The mutant overproduced catalase A more than 50-fo1d compared with the wild type. The mutation locus catRI was mapped closed to the mthB2 locus by genetic crossings. An ordered cosmid library of S. coelicolor encompassing the mthB2 locus was used to isolate the regulator gene (catR) which represses catalase overproduction when introduced into HR4O. A candidate catR gene was found to encode a Fur-like protein of 138 amino acids (15319 Da).

• Microbiology and Biotechnology Letters
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• v.22 no.5
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• pp.538-543
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• 1994

Effect of partial oxygen pressure on the cell growth and the activities of oxidative defense enzymes were measured in the continuous culture of Streptomyces coelicolor. Both the wild type and the mutant strain resistant to hydrogen peroxide were cultured and the dry cell weight of the two cultures were measured at different oxygen tensions. Growth of the wild type was inhibited by oxygen at above 0.5 vvm. Growth of the hydrogen peroxide resistant mutant was stimulated by pure oxygen at 0.5 vvm but was inhibited by oxygen at 1.0 vvm. Therefore, growth of the hydrogen peroxide resistant mutant was less affected by the deleterious oxidative stress of oxygen. Activities of the several defense enzymes were also measured at different oxygen tensions. Activities of catalase and glucose-6-phosphate dehydrogenase increased significantly as oxygen pressure increased in the wild type culture. In the mutant, however, increase in those enzyme activities was not obvious whereas the uninduced levels of the above enzymes were higher than those of wild type. As judged by Western blotting, the amount of the major catalase increased as the oxygen pressure increased. This indicates that the induction of the catalase activity by oxygen pressure is mostly due to the increase in the expression level for the major catalase.

• Journal of Microbiology and Biotechnology
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• v.24 no.8
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• pp.1118-1122
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• 2014

The present study shows that DR1114 (Hsp20), a small heat shock protein of the radiation-resistant bacterium Deinococcus radiodurans, enhances tolerance to hydrogen peroxide ($H_2O_2$) stress when expressed in Escherichia coli. A protein profile comparison showed that E. coli cells overexpressing D. radiodurans Hsp20 (EC-pHsp20) activated the redox state proteins, thus maintaining redox homeostasis. The cells also showed increased expression of pseudouridine (psi) synthases, which are important to the stability and proper functioning of structural RNA molecules. We found that the D. radiodurans mutant strain, which lacks a psi synthase (DR0896), was more sensitive to $H_2O_2$ stress than wild type. These suggest that an increased expression of proteins involved in the control of redox state homeostasis along with more stable ribosomal function may explain the improved tolerance of EC-pHsp20 to $H_2O_2$ stress.

• Molecules and Cells
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• v.21 no.3
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• pp.389-394
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• 2006

Human seven-in-absentia (SIAH)-interacting protein (SIP) is a component of the E3 ligase complex targeting beta-catenin for destruction. Arabidopsis has one SIP protein (AtSIP) with 32% amino acid sequence identity to SIP. To investigate the functions of AtSIP, we isolated an atsip knockout mutant, and generated transgenic plants overexpressing AtSIP. The growth rates and morphologies of the atsip and transgenic plants were indistinguishable from those of wild type. However, atsip plants were more susceptible to Pseudomonas syringae infection, and the transgenic plants overexpressing AtSIP were more resistant. Consistent with this, RNA blot analysis showed that the AtSIP gene is strongly induced by wounding and hydrogen peroxide treatment. In addition, when plants were infected with P. syringae, AtSIP was transiently induced prior to PR-1 induction. These observations show that Arabidopsis AtSIP plays a role in resistance to pathogenic infection.

• Journal of Microbiology
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• v.33 no.4
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• pp.339-343
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• 1995

We isolated a 10 kb Bam HI fragment originated from the chromosome of a $H_2O$$^2$-resistant mutant strain of Streptomyces coelicolor, which confer $H_2O$$^2$-resistance to S. lividance upon transformation. Among various subclones ot 10kb Bam HI fragment tested for their $H_2O$$^2$-resistant phenotype in S. lividans, a subclone containing 5.2 kb Bam HI-BglII fragment was found to be responsible for $H_2O$$^2$-resistance. The plasmid containing this 5.2 kb fragment was then transformed into S. coellicolor A3(2) at early and tested for their phenotype of $H_2O$$^2$-resistance and the change in various enzymes whose activity can be stained in the gel. We found out that the 5.2 kb insert DNA conferred $H_2O$$^2$-resisstance in S. coelicolor A3(2) at early phase of cell growth. The presence of this DNA also resulted in higher level of peroxidase compared with the wild type cell containing parental vector (pIJ702) only. Esterase activity was also higher in this clone. However, alcohol dehydrogenase activity decreased compared with the wild type. These results suggest that the presence of a gene in 5.2 kb BamHI-BglII DNA fragment causes multiple changes in S. coelicolor related to its response against hydrogen peroxide. The result also implies that not only peroxidase but also esterase may function in the defencse meahsnism agianst $H_2O$$^2$-.