page_title: FNR regulon
section_title: Genes regulated by FNR
hierarchical_section_title: FNR regulon / Genes regulated by FNR
caption_attribution_description: English: image formed using inscape
context_page_description: The fnr gene of Escherichia coli encodes a transcriptional activator which is required for the expression of a number of genes involved in anaerobic respiratory pathways. The FNR protein of E. coli is an oxygen – responsive transcriptional regulator required for the switch from aerobic to anaerobic metabolism.
  The fnr gene is expressed under both aerobic and anaerobic conditions and is subject to autoregulation and repression by glucose, particularly during anaerobic growth.
  The functional state of FNR is determined by a inactivation of FNR by O₂, and a slow reactivation with glutathione as the reducing agent.
context_section_description: FNR represents the master-switch which ensures that aerobic respiration is used in preference to anaerobic respiratory metabolism or fermentation, simply because important anaerobic genes are not expressed unless FNR is in its active (anaerobic) form. FNR is a very important transcriptional factor that is involved in the regulation of synthesis of many genes. 
  Important groups of FNR-regulated genes of E. coli
  Active FNR protein activates and represses target genes in response to anaerobiosis.  It also represses the aerobic genes, cytochrome d and o oxidase, and NADH dehydrogenase II. It acts as a positive regulator of genes expressed under anaerobic fermentative conditions such as aspartase, formate hydrogenase, fumarate reductase, and pyruvate formate lyase.
caption: Regulation of Nar and arfM gene by FNR(activated)
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