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FNR is a direct oxygen sensor having a biphasic response curve
Author(s) -
Jordan Peter A.,
Thomson Andrew J.,
Ralph Edward T.,
Guest John R.,
Green Jeffrey
Publication year - 1997
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(97)01219-2
Subject(s) - electron paramagnetic resonance , dimer , chemistry , ferric , iron–sulfur cluster , molar ratio , sulfur , ion , mössbauer spectroscopy , cluster (spacecraft) , crystallography , molecule , kinetics , dna , oxygen , inorganic chemistry , biochemistry , nuclear magnetic resonance , enzyme , catalysis , organic chemistry , physics , quantum mechanics , computer science , programming language
FNR is a transcription regulator that controls the expression of target genes in response to anoxia. Anaerobiosis is accompanied by the acquisition of two [4Fe‐4S] 2+ clusters per FNR dimer and the ability to bind DNA site‐specifically. Oxidation of the [4Fe‐4S] 2+ form of FNR by O 2 produced a non‐DNA‐binding, transcriptionally inactive form which also contains an iron‐sulfur cluster, recently identified by Mossbauer spectroscopy as a [2Fe‐2S] cluster (Khoroshilova et al., 1997, PNAS. 94, 6078). Complete conversion needed at least 2.5–3.0 molecules of O 2 per [4Fe‐4S] 2+ cluster. Using sub‐stoicheiometric amounts of air‐saturated buffer, stable equilibria were established in which the [4Fe‐4S] 2+ and [2Fe‐2S] 2+ forms co‐exist and no EPR detectable free ferric ions were released. In contrast, a 20‐fold molar excess K 3 Fe(CN) 6 was required to oxidise the [4Fe‐4S] 2+ cluster and in this case, ferric ions were released. FNR is therefore a sensitive O 2 sensor.