A complex generally comprising an FAD-containing component that also binds the carboxylate substrate (A subunit), a component that contains three different iron-sulfur centers [2Fe-2S], [4Fe-4S], and [3Fe-4S] (B subunit), and a hydrophobic membrane-anchor component (C, or C and D subunits) that is also the site of the interaction with quinones. The enzyme is found in the inner mitochondrial membrane in eukaryotes and the plasma membrane of bacteria and archaea, with the hydrophilic domain extending into the mitochondrial matrix and the cytoplasm, respectively. Under aerobic conditions the enzyme catalyses succinate oxidation, a key step in the citric acid (TCA) cycle, transferring the electrons to quinones in the membrane, thus linking the TCA cycle with the aerobic respiratory chain (where it is known as complex II). Under anaerobic conditions the enzyme functions as a fumarate reductase, transferring electrons from the quinol pool to fumarate, and participating in anaerobic respiration with fumarate as the terminal electron acceptor. The enzyme interacts with the quinone produced by the organism, such as ubiquinone, menaquinone, caldariellaquinone, thermoplasmaquinone, rhodoquinone etc. Some of the enzymes contain two heme subunits in their membrane anchor subunit. These enzymes catalyse an electrogenic reaction and are thus classified as EC 7.1.1.12, succinate dehydrogenase (electrogenic, proton-motive force generating).
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SYSTEMATIC NAME
IUBMB Comments
succinate:quinone oxidoreductase
A complex generally comprising an FAD-containing component that also binds the carboxylate substrate (A subunit), a component that contains three different iron-sulfur centers [2Fe-2S], [4Fe-4S], and [3Fe-4S] (B subunit), and a hydrophobic membrane-anchor component (C, or C and D subunits) that is also the site of the interaction with quinones. The enzyme is found in the inner mitochondrial membrane in eukaryotes and the plasma membrane of bacteria and archaea, with the hydrophilic domain extending into the mitochondrial matrix and the cytoplasm, respectively. Under aerobic conditions the enzyme catalyses succinate oxidation, a key step in the citric acid (TCA) cycle, transferring the electrons to quinones in the membrane, thus linking the TCA cycle with the aerobic respiratory chain (where it is known as complex II). Under anaerobic conditions the enzyme functions as a fumarate reductase, transferring electrons from the quinol pool to fumarate, and participating in anaerobic respiration with fumarate as the terminal electron acceptor. The enzyme interacts with the quinone produced by the organism, such as ubiquinone, menaquinone, caldariellaquinone, thermoplasmaquinone, rhodoquinone etc. Some of the enzymes contain two heme subunits in their membrane anchor subunit. These enzymes catalyse an electrogenic reaction and are thus classified as EC 7.1.1.12, succinate dehydrogenase (electrogenic, proton-motive force generating).
a key membrane complex in the tricarboxylic acid cycle that catalyzes the oxidation of succinate to fumarate in the mitochondrial matrix as succinate dehydrogenase
electrons are transferred from succinate to ubiquinone through the buried prosthetic groups FAD, [2Fe-2S] cluster, [4Fe-4S] cluster [3Fe-4S] cluster and heme, which form an integral part of the complex
a key membrane complex in the tricarboxylic acid cycle that catalyzes the oxidation of succinate to fumarate in the mitochondrial matrix as succinate dehydrogenase
complex II is comprised of two hydrophilic proteins, flavoprotein (Fp) and iron-sulfur protein (Ip), and two transmembrane proteins (CybL and CybS), as well as prosthetic groups required for electron transfer from succinate to ubiquinone
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CRYSTALLIZATION (Commentary)
ORGANISM
UNIPROT
LITERATURE
hanging drop method, crystal structure of complex II from porcine heart at 2.4 A resolution and its complex structure with inhibitors 3-nitropropionate and 2-thenoyltrifluoroacetone at 3.5 A resolution
molecular docking, molecular dynamics simulation, and molecular mechanics/Poisson-Boltzmann surface area calculations for complexes with carboxamide inhibitors. The acid moiety of carboxamide fungicides inserts into the ubiquinone binding site of SQR, forming van der Waals interactions with subunit C residues R46, S42, and subunit B residues I218, and P169, while the amine moiety extends to the mouth of the Q-site, forming van der Waals interactions with subunit C residues W35, I43, and I30. The carbonyl oxygen atom of the carboxamide forms hydrogen bonds with subunit B W173 and subunit DY91
partially purified enzyme, crystal growth in ammonium sulfate preparation precipitate, X-ray diffraction structure determination and analysis at 2.4 A resolution