Journal of Microbiology

Research Support, Non-U.S. Gov't

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

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.

Identification and characterization of pH-regulated genes in saccharomyces cerevisiae: Hong, Sung Ki , Choi, Eui Yul; J. Microbiol. 1996;34(4):327-333.

Abstract: Yeast, like many other microbes, encounters large variations in ambient pH in their natural environments. Microorganisms capable of growing over a wide pH range require a versatile, efficient pH homeostatic mechanism protecting intracellular processes against extremes of pH. In several organisms, fusions to the bacterial lacZ gene have been extremely useful for the identification of genes expressed at different time during the life cycle or under different growth conditions. In this study, using the lacZ gene screening system, we surveyed a large number of yeast strains with lacZ insertion to identify genes regulated by pH. A yeast genomic library was constructed and inserted with lacZ by a shuttle mutagenesis procedure. The yeast transformants were individually picked up with a toothpick, replica-plated, and grown in alkaline pH medium. Among the 35,000 colonies screened, 10 candidate strains were identified initially by the β-gal assay. We finally confirmed two yeast strains carrying the genes whose expression are strictly dependent on pH of growth medium. One of the fusions showing a 10-fodl induction in expression level in response to alkali pH was selected and further characterized. The pH-regulated gene was cloned by inverse PCR and a partial sequence of the gene was determined. Identification and characterization of the gene is currently under investigation.

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