Regulation of V‐nitrogenase genes in Anabaena variabilis by RNA processing and by dual repressors. Issue 2 (21st March 2013)

• Record Type: Journal Article
• Authors: Pratte, Brenda S.; Sheridan, Ryan; James, Jessie A.; Thiel, Teresa
• Is Part Of: Molecular microbiology. Volume 88:Issue 2(2013)
• Page Start: 413
• Page End: 424
• Publication Date: 2013-03-21
• Subjects: Molecular microbiology -- Periodicals; 572.829
• DOI: 10.1111/mmi.12197
• Languages: English
• ISSNs: 0950-382X

Abstract

<abstract abstract-type="main"> <title>Summary</title> <p> <italic>Anabaena variabilis</italic> ATCC 29413 fixes nitrogen in specialized cells called heterocysts using either a Mo‐nitrogenase or a V‐nitrogenase. V‐nitrogenase structural genes, <italic>vnfDGK</italic>, as well as <italic>vnfEN</italic> form an operon with <italic>ava4025</italic>, located upstream of <italic>vnfDG</italic> that is repressed by fixed nitrogen and by Mo. The <italic>ava4025</italic>‐<italic>vnfDGKEN</italic> operon is under the control of a Mo‐repressible promoter located nearly 600 bp upstream of <italic>ava4025</italic>. Levels of <italic>vnfDG</italic> transcript were about 500‐fold higher than <italic>ava4025</italic>, the first gene of the operon. This may be the result of RNA processing at a site 87 bp upstream of <italic>vnfDG</italic> that was initially identified as the transcription start site. A strain with a deletion in the coding region of <italic>ava4025</italic> grew diazotrophically with Mo or with V. Two similar proteins, VnfR1 and VnfR2, whose genes are located some distance from the <italic>ava4025</italic>‐<italic>vnfDGKEN</italic> operon, each repressed transcription from the <italic>ava4025</italic>‐<italic>vnfDGKEN</italic> promoter and a mutant lacking both VnfR1 and VnfR2 made the V‐nitrogenase in the presence of Mo. Overexpression of the V‐nitrogenase in the double <italic>vnfR1 vnfR2</italic> mutant resulted in decreased activity of the Mo‐nitrogenase. VnfR1 bound specifically, <italic>in vitro</italic>, to a region upstream of the <italic>ava4025</italic> promoter.</p> </abstract>