Increasing industrial applications of selenium as well as its use in supplementation studies at elevated but sublethal concentrations warrant further investigation into the mechanism(s) of selenium toxicity. Through use of an Escherichia coli luxAB transcriptional gene fusion library, our laboratory identified two clones whose luminescence increased in the presence of sodium selenite. The clones were designated strains LF20113 and LF20116. Cloning and sequencing portions of the two genes revealed that luxAB had inserted within two previously uncharacterized open reading frames, designated o219 and o393, which we have now named ginS and gutS, respectively. Transcription from these genes in response to increasing concentrations of sodium selenite was confirmed by RNA dot blot analysis. Primer extension analysis of the predicted promoter region of ginS revealed that the promoter was within the previously predicted protein coding sequence and thus, this gene is smaller than originally suspected. Expression of the GinS polypeptide in vivo demonstrated that the protein is approximately 22 kDa, which is also consistent with the smaller coding sequence. Homology searches have also shown that this protein is a member of the DedA family of proteins whose functions remain unknown. We have shown that three genes are down-regulated upon expression of the ginS gene product. These genes are clpX, b1169 , and gspC, and may indicate the involvement of ginS in a new pathway of protein transport in response to selenite exposure. Moreover, strain LF20113 is more sensitive to elevated concentrations of sodium selenite than the parental strain indicating a protective function for the gene. Characterization of the second selenite-responsive gene, gutS, revealed that this gene is not only transcribed in the presence of selenite, but also tellurite, as shown by measurement of luminescence from strain LF20116 as well as by measurement of transcription of gutS by RNA dot blot analysis. Exp
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.36598 |
| Date | January 1999 |
| Creators | Guzzo, Julie. |
| Contributors | DuBow, Michael S. (advisor) |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Microbiology and Immunology.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 001740475, proquestno: NQ64566, Theses scanned by UMI/ProQuest. |
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