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A constitutively expressed pair of rpoE2-chrR2 in Azospirillum brasilense Sp7 is required for survival under antibiotic and oxidative stress.
MedLine Citation:
PMID:  23059974     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Extracytoplasmic function (ECF) sigma factors (σE) are known to bring about changes in gene expression to enable bacteria to adapt to different stresses. The Azospirillum brasilense Sp245 genome harbours 9 genes encoding σE of which 2 are adjacent to the genes encoding ChrR-type zinc binding anti-sigma (ZAS) factors. We describe here the role and regulation of a new pair of rpoE-chrR, which was found in the genome of A. brasilense Sp7 in addition to the previously described rpoE-chrR pair (designated as rpoE1-chrR1). The rpoE2-chrR2 pair is also cotranscribed and their products show protein-protein interaction. The -10 and -35 promoter elements of rpoE2-chrR2 and rpoE1-chrR1 were similar but not identical. Unlike the promoter of rpoE1-chrR1, rpoE2-chrR2 promoter was neither autoregulated nor induced by oxidative stress. Inactivation of chrR2 or overexpression of rpoE2 in A. brasilense Sp7 resulted in an overproduction of carotenoids. It also conferred resistance to oxidative stresses and antibiotics. By controlling the synthesis of carotenoids, initiation and elongation of translation, protein folding and purine biosynthesis, RpoE2 seems to play a crucial role in preventing and repairing the cellular damage caused by the oxidative stress. Lack of autoregulation and constitutive expression of rpoE2-chrR2 suggest that RpoE2-ChrR2 may provide a rapid mechanism to cope with oxidative stress wherein 1O2 mediated dissociation of RpoE2-ChrR2 complex might release RpoE2 to drive the expression of its target genes.
Authors:
Namrata Gupta; Santosh Kumar; Mukti Nath Mishra; Anil Kumar Tripathi
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-10-11
Journal Detail:
Title:  Microbiology (Reading, England)     Volume:  -     ISSN:  1465-2080     ISO Abbreviation:  Microbiology (Reading, Engl.)     Publication Date:  2012 Oct 
Date Detail:
Created Date:  2012-10-12     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9430468     Medline TA:  Microbiology     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Affiliation:
School of Biotechnology, Banaras Hindu University, Varanasi;
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