Journal of Microbiology

Review

[Minireview] Unraveling new functions of superoxide dismutase using yeast model system: Beyond its conventional role in superoxide radical scavenging: Woo-Hyun Chung ,; J. Microbiol. 2017;55(6):409-416. Published online March 9, 2017; DOI: https://doi.org/10.1007/s12275-017-6647-5

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39 Citations

Abstract: To deal with chemically reactive oxygen molecules constantly threatening aerobic life, cells are readily equipped with elabo-rate biological antioxidant systems. Superoxide dismutase is a metalloenzyme catalytically eliminating superoxide radi-cal as a first-line defense mechanism against oxidative stress. Multiple different SOD isoforms have been developed through-out evolution to play distinct roles in separate subcellular com-partments. SOD is not essential for viability of most aerobic organisms and intriguingly found even in strictly anaerobic bacteria. Sod1 has recently been known to play important roles as a nuclear transcription factor, an RNA binding pro-tein, a synthetic lethal interactor, and a signal modulator in glucose metabolism, most of which are independent of its canonical function as an antioxidant enzyme. In this review, recent advances in understanding the unconventional role of Sod1 are highlighted and discussed with an emphasis on its genetic crosstalk with DNA damage repair/checkpoint path-ways. The budding yeast Saccharomyces cerevisiae has been successfully used as an efficient tool and a model organism to investigate a number of novel functions of Sod1.

Research Support, Non-U.S. Gov'ts

Expression and Characterization of an Iron-Containing Superoxide Dismutase from Burkholderia pseudomallei: Min-Hee Cho , Yong-Woo Shin , Jeong-Hoon Chun , Kee-Jong Hong , Byoung-Kuk Na , Gi-eun Rhie , Baik-Lin Seong , Cheon-Kwon Yoo; J. Microbiol. 2012;50(6):1029-1033. Published online December 30, 2012; DOI: https://doi.org/10.1007/s12275-012-2267-2

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Abstract: A superoxide dismutase (SOD) gene from Burkholderia pseudomallei, the causative agent of melioidosis, was cloned and expressed in Escherichia coli, and its product was functionally and physically characterized. The gene has an open-reading frame of 579 bp. The deduced amino acid sequence has 192 residues with a calculated molecular mass of ~22 kDa. Sequence comparison with other bacterial SODs showed that the protein contains typical metal-binding motifs and other Fe-SOD-conserved residues. The sequence has substantial similarity with other bacterial Fe-SOD sequences. The enzymatic activity of the expressed protein was inhibited by hydrogen peroxide but not by sodium azide or potassium cyanide, attributes that indeed are characteristic of typical bacterial Fe-SODs. Western blotting with antiserum against the recombinant Fe-SOD revealed that it is expressed in B. pseudomallei. Transformed E. coli that expressed the Fe-SOD had significantly increased SOD activity and was highly tolerant to paraquat-mediated replication inhibition, compared to transformed cells carrying an empty vector. Our results provide a basis for further biochemical characterization of the enzyme and elucidation of its role in the pathogenesis of B. pseudomallei.

Molecular Cloning, Purification, and Characterization of a Superoxide Dismutase from a Fast-Growing Mycobacterium sp. Strain JC1 DSM 3803: Ji-Sun Nam , Jee-Hyun Yoon , Hyun-Il Lee , Si Wouk Kim , Young-Tae Ro; J. Microbiol. 2011;49(3):399-406. Published online June 30, 2011; DOI: https://doi.org/10.1007/s12275-011-1046-9

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8 Citations

Abstract: A cytosolic superoxide dismutase (SOD) was purified and characterized from a fast-growing Mycobacterium sp. strain JC1 DSM 3803 grown on methanol. The native molecular weight of the purified SOD was estimated to be 48 kDa. SDS-PAGE revealed a subunit of 23 kDa, indicating that the enzyme is a homodimer. The enzyme activity was inhibited by H2O2 and azide. The purified SOD contained 1.12 and 0.56 g-atom of Mn and Fe per mol of enzyme, respectively, suggesting that it may be a Fe/Mn cambialistic SOD. The apo-SOD reconstitution study revealed that Mn salts were more specific than Fe salts in the SOD activity. The gene encoding the SOD was identified from the JC1 cosmid genomic library by PCR screening protocol. The cloned gene, sodA, had an open reading frame (ORF) of 624 nt, encoding a protein with a calculated molecular weight of 22,930 Da and pI of 5.33. The deduced SodA sequence exhibited 97.6% identity with that of Mycobacterium fortuitum Mn-SOD and clustered with other mycobacterial Mn-SODs. A webtool analysis on the basis of SOD sequence and structure homologies predicted the SOD as a tetrameric Mn-SOD, suggesting that the protein is a dimeric Mn-SOD having tetramer-specific sequence and structure characteristics.

Isolation and Characterization of the sod2+ Gene Encoding a Putative Mitochondrial Manganese Superoxide Dismutase in Schizosaccharomyces pombe: Jae-Hoon Jeong , Eun-Soo Kwon , Jung-Hye Roe; J. Microbiol. 2001;39(1):37-41.

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Abstract: The fission yeast Schizosaccharomyces pombe contains two distinct superoxide dismutase (SOD) activities, one in the cytosol encoded by the sod1+ gene and the other in mitochondria. The sod2+ gene encoding putative mitochondrial manganese superoxide dismutase (MnSOD) was isolated from the S. pombe genomic library using a PCR fragment as the probe. The nucleotide sequence of the sod2+ gene and its flanking region (4051 bp HindIII fragment) was determined. An intron of 123 nt in size was predicted and confirmed by sequencing the cDNA following reverse transcription PCR. The predicted Sod2p consists of 218 amino acid residues with a molecular mass of 24,346 Da. The deduced amino acid sequence showed a high degree of homology with other MnSODs, especially in the metal binding residues at the active site and their relative positions. The transcriptional start site was mapped by primer extension at 231 nt upstream from the ATG codon. A putative TATA box (TATAAAA) was located 58 nt upstream from the transcriptional start site and putative polyadenylation sites were located at 1000, 1062, and 1074 nt downstream from the ATG start codon.

Molecular Cloning of the Superoxide Dismutase Gene from Orientia tsutsugamushi, the Causative Agent of Scrub Typhus: Ji-Hyun Yun , Young-Sang Koh , Se-Jae Kim; J. Microbiol. 2002;40(2):151-155.

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Abstract: A superoxide dismutase (SOD) gene from the obligate intracellular bacterium Orientia tsutsugamushi has been cloned by using the polymerase chain reaction with degenerate oligonucleotide primers corresponding to conserved regions of known SODs. Nucleotide sequencing revealed that the predicted amino acid sequence was significantly more homologous to known iron-containing SODs (FeSOD) than to manganese-containing SODs (MnSOD). Conserved regions in bacterial FeSOD could also be seen. Isolation of the oriential SOD gene may provide an opportunity to examine its role in the intracellular survival of this bacterium.

Regulation of the sufABCDSE Operon by Fur: Joon-Hee Lee , Won-Sik Yeo , Jung-Hye Roe; J. Microbiol. 2003;41(2):109-114.

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Abstract: A promoter that is inducible by paraquat and menadione, the superoxide generators, independently of soxRS has been found in front of the sufABCDSE operon in Escherichia coli. Based on the observation that SufA is a holomog of IscA that functions in the assembly of iron sulfur cluster and the sufA promoter (sufAp) contains a putative Fur-binding consensus, we investigated whether this gene is regulated by Fur, a ferric uptake regulator. When examined in several sufAp-lacZ chromosomal fusion strains, sufAp was induced by EDTA, an iron chelator and a well-known Fur-inducer. The basal level of sufA expression increased dramatically in fur mutant, suggesting repression of sufAp by Fur. The derepression in fur mutant and EDTA-induction of sufA expression required nucleotides up to -61, where a putative Fur box is located. Purified Fur protein bound to the DNA fragment containing the putative Fur box between -35 and -10 promoter elements. The regulation by Fur and menadione induction of sufAp acted independently. The rpoS mutation increased sufA induction by menadione, suggesting that the stationary sigma factor RpoS acts negatively on sufA induction.

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