The enzyme contains molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters and two heme b groups. Formate dehydrogenase-N oxidizes formate in the periplasm, transferring electrons via the menaquinone pool in the cytoplasmic membrane to a dissimilatory nitrate reductase (EC 1.7.5.1), which transfers electrons to nitrate in the cytoplasm. The system generates proton motive force under anaerobic conditions .
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SYSTEMATIC NAME
IUBMB Comments
formate:quinone oxidoreductase
The enzyme contains molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters and two heme b groups. Formate dehydrogenase-N oxidizes formate in the periplasm, transferring electrons via the menaquinone pool in the cytoplasmic membrane to a dissimilatory nitrate reductase (EC 1.7.5.1), which transfers electrons to nitrate in the cytoplasm. The system generates proton motive force under anaerobic conditions [3].
in the proton motive system of the formate dehydrogenase the donor oxidation and quinone reduction sites are located at opposite sides of the membrane. The formate dehydrogenase (Fdh-N or FdnGHI complex) and nitrate reductase A (NarA or NarGHI complex) together form the paradigmatic Fdh-Nar full redox loop
the synthesis of formate dehydrogenase-N and nitrate reductase is coordinately regulated by anaerobiosis and nitrate. Upstream sequence elements required for nitrate and anaerobic induction of fdn (formate dehydrogenase-N) operon expression are localized
Fdh-N and dissimilatory nitrate reductase (Nar) can form a redox loop where proton motive force generation is best described as the sum of the following two effects. 1. Two protons, which are taken up from the cytoplasm at the Fdh-N menaquinone reduction site, are translocated across the membrane and released to the periplasm from the menaquinol oxidation site in Nar. 2. Two electrons are transferred from the formate oxidation site in periplasm to the NO3- reduction site in cytoplasm. This is not accompanied by an actual proton translocation across the membrane but generates a membrane potential, which is equivalent to 2 H+ translocation across the membrane. The result is consistent with the measured ratio of proton translocation to electron transfer in this system. In the catalytic site, the Mo directly takes up electrons from the bound substrate. These electrons are transferred to the beta subunit though the [4Fe4S] cluster (FeS-0) in the alpha subunit. The four [4Fe-4S] clusters in the beta subunit, which are aligned in the order of FeS-1, FeS-4, FeS-2, and FeS-3, connect the alpha and gamma subunits like an electric wire. From FeS-3 of the beta subunit, electrons are transferred to heme bP (P for periplasm) in the gamma subunit and then across the membrane to heme bC (C for cytoplasm). Menaquinone binds to a histidine ligand (Hisg169) of heme bC and can directly accept electrons through this residue. The electron transfer from formate (standard redox potential, 2420 mV) to menaquinone (275 mV) is a highly exergonic reaction, allowing the electron transfer against the membrane potential
Fdh-N and dissimilatory nitrate reductase (Nar) can form a redox loop where proton motive force generation is best described as the sum of the following two effects. 1. Two protons, which are taken up from the cytoplasm at the Fdh-N menaquinone reduction site, are translocated across the membrane and released to the periplasm from the menaquinol oxidation site in Nar. 2. Two electrons are transferred from the formate oxidation site in periplasm to the NO3- reduction site in cytoplasm. This is not accompanied by an actual proton translocation across the membrane but generates a membrane potential, which is equivalent to 2 H+ translocation across the membrane. The result is consistent with the measured ratio of proton translocation to electron transfer in this system. In the catalytic site, the Mo directly takes up electrons from the bound substrate. These electrons are transferred to the beta subunit though the [4Fe4S] cluster (FeS-0) in the alpha subunit. The four [4Fe-4S] clusters in the beta subunit, which are aligned in the order of FeS-1, FeS-4, FeS-2, and FeS-3, connect the alpha and gamma subunits like an electric wire. From FeS-3 of the beta subunit, electrons are transferred to heme bP (P for periplasm) in the gamma subunit and then across the membrane to heme bC (C for cytoplasm). Menaquinone binds to a histidine ligand (Hisg169) of heme bC and can directly accept electrons through this residue. The electron transfer from formate (standard redox potential, 2420 mV) to menaquinone (275 mV) is a highly exergonic reaction, allowing the electron transfer against the membrane potential
in the proton motive system of the formate dehydrogenase the donor oxidation and quinone reduction sites are located at opposite sides of the membrane. The formate dehydrogenase (Fdh-N or FdnGHI complex) and nitrate reductase A (NarA or NarGHI complex) together form the paradigmatic Fdh-Nar full redox loop
the synthesis of formate dehydrogenase-N and nitrate reductase is coordinately regulated by anaerobiosis and nitrate. Upstream sequence elements required for nitrate and anaerobic induction of fdn (formate dehydrogenase-N) operon expression are localized
the structure demonstrates 11 redox centers, including molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters, two heme b groups, and a menaquinone analog. These redox centers are aligned in a single chain, which extends almost 90 A through the enzyme. In the catalytic site, the Mo directly takes up electrons from the bound substrate. These electrons are transferred to the beta subunit through the [4Fe4S] cluster (FeS-0) in the alpha subunit. The four [4Fe-4S] clusters in the beta subunit, which are aligned in the order of FeS-1, FeS-4, FeS-2, and FeS-3, connect the alpha and gamma subunits like an electric wire. From FeS-3 of the beta subunit, electrons are transferred to heme bP (P for periplasm) in the gamma subunit and then across the membrane to heme bC (C for cytoplasm). Menaquinone binds to a histidine ligand (Hisg169) of heme bC and can directly accept electrons through this residue
the low-potential cytochrome b of the formate dehydrogenase complex is an essential component in the electron transport from formate to menaquinone. The 25000 Da subunit represents cytochrome b
the structure demonstrates 11 redox centers, including molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters, two heme b groups, and a menaquinone analog. These redox centers are aligned in a single chain, which extends almost 90 A through the enzyme. In the catalytic site, the Mo directly takes up electrons from the bound substrate. These electrons are transferred to the beta subunit through the [4Fe4S] cluster (FeS-0) in the alpha subunit. The four [4Fe-4S] clusters in the beta subunit, which are aligned in the order of FeS-1, FeS-4, FeS-2, and FeS-3, connect the alpha and gamma subunits like an electric wire. From FeS-3 of the beta subunit, electrons are transferred to heme bP (P for periplasm) in the gamma subunit and then across the membrane to heme bC (C for cytoplasm). Menaquinone binds to a histidine ligand (Hisg169) of heme bC and can directly accept electrons through this residue
the structure demonstrates 11 redox centers, including molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters, two heme b groups, and a menaquinone analog. These redox centers are aligned in a single chain, which extends almost 90 A through the enzyme. In the catalytic site, the Mo directly takes up electrons from the bound substrate. These electrons are transferred to the beta subunit through the [4Fe4S] cluster (FeS-0) in the alpha subunit. The four [4Fe-4S] clusters in the beta subunit, which are aligned in the order of FeS-1, FeS-4, FeS-2, and FeS-3, connect the alpha and gamma subunits like an electric wire. From FeS-3 of the beta subunit, electrons are transferred to heme bP (P for periplasm) in the gamma subunit and then across the membrane to heme bC (C for cytoplasm). Menaquinone binds to a histidine ligand (Hisg169) of heme bC and can directly accept electrons through this residue
the structure demonstrates 11 redox centers, including molybdopterin-guanine dinucleotides, five [4Fe-4S] clusters, two heme b groups, and a menaquinone analog. These redox centers are aligned in a single chain, which extends almost 90 A through the enzyme
the enzyme contains selenocysteine. Both stability and specific nucleotide sequences of a mRNA stem-loop likely contribute to the appropriate mRNA context for selenocysteine incorporation into the fdnG gene product
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OXIDATION STABILITY
ORGANISM
UNIPROT
LITERATURE
formate dehydrogenase activity is lost when the enzyme is exposed to oxygen. This instability is enhanced in low ionic strength buffers, detergents, at temperatures above 0°C, and at pH greater than 7
formate dehydrogenase is extremely sensitive to inactivation by oxygen in the presence of formate. Purified formate dehydrogenase is completely inactivated by aerobic incubation in 75 mM sodium phosphate, pH 7, for 1 h at 20°C in the presence of 50 mM formate, while only 40% of the activity is lost when the same incubation is carried out in the absence of formate. No activity is lost when the same incubation is carried out anaerobically even in the presence of formate
Localization of upstream sequence elements required for nitrate and anaerobic induction of fdn (formate dehydrogenase-N) operon expression in Escherichia coli K-12
Nitrate-inducible formate dehydrogenase in Escherichia coli K-12. I. Nucleotide sequence of the fdnGHI operon and evidence that opal (UGA) encodes selenocysteine
J. Biol. Chem.
266
22380-22385
1991
Escherichia coli K-12 (P24183 and P0AAJ3 and P0AEK7), Escherichia coli K-12
Nitrate-inducible formate dehydrogenase in Escherichia coli K-12. II. Evidence that a mRNA stem-loop structure is essential for decoding opal (UGA) as selenocysteine