FNR-mediated regulation of hyp expression in Escherichia coli.
The hypA-E operon is involved in the maturation of all three NiFe hydrogenases in Escherichia coli. Two hyp promoters have been described; a sigma54-dependent promoter upstream of hypA, and a sigma70-dependent promoter (PhypA) within the hypA coding region. Here it is shown that the oxygen-responsive transcription factor FNR regulates PhypA under anaerobic conditions only. PhypA does not possess a canonical FNR recognition sequence, but two FNR half-sites are present. Studies using PHYPA::lacZ fusions carrying lesions in one or both FNR half-sites indicated that although some residual anaerobic activity was retained by the promoter containing only the downstream FNR half-site, both half-sites are required for maximal PhypA activity in vivo. In vitro gel retardation analysis suggested that the primary interaction occurs at the downstream FNR half-site. Possible explanations for these observations and the implications for other FNR-regulated promoters are discussed.
Messenger
Sarah L
SL
The Krebs Institute for Biomolecular Research, Department of Molecular Biology and Biotechnology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
Green
Jeffrey
J
D000693:Anaerobiosis; D001483:Base Sequence; D004926:Escherichia coli / Q000235:genetics*; D029968:Escherichia coli Proteins / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D006864:Hydrogenase / Q000235:genetics* / Q000378:metabolism; D007506:Iron-Sulfur Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016296:Mutagenesis; D009876:Operon; D010100:Oxygen / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics
D029968:Escherichia coli Proteins; C060704:FNR protein, E coli; D007506:Iron-Sulfur Proteins; D012808:Sigma Factor; D014157:Transcription Factors; C043296:nickel-iron hydrogenase; D006864:Hydrogenase; D010100:Oxygen