The cytochrome complex, or cyt c, is a small hemeprotein found loosely associated with the inner membrane of the mitochondrion where it plays a critical role in cellular respiration. It transfers electrons between Complexes III and IV. Cytochrome c is highly water-soluble, unlike other cytochromes. It is capable of undergoing oxidation and reduction as its iron atom converts between the ferrous and ferric forms, but does not bind oxygen. It also plays a major role in cell apoptosis. In humans, cytochrome c is encoded by the CYCS gene.
An antiporter (also called exchanger or counter-transporter) is a cotransporter and integral membrane protein involved in secondary active transport of two or more different molecules or ions across a phospholipid membrane such as the plasma membrane in opposite directions, one into the cell and one out of the cell. Na+/H+ antiporters have been reviewed.
petite (ρ–) is a mutant first discovered in the yeast Saccharomyces cerevisiae. Due to the defect in the respiratory chain, 'petite' yeast are unable to grow on media containing only non-fermentable carbon sources and form small colonies when grown in the presence of fermentable carbon sources. The petite phenotype can be caused by the absence of, or mutations in, mitochondrial DNA, or by mutations in nuclear-encoded genes involved in oxidative phosphorylation. A neutral petite produces all wild type progeny when crossed with wild type.
P700, or photosystem I primary donor, is the reaction-center chlorophyll a molecular dimer associated with photosystem I in plants, algae, and cyanobacteria.
Sulfite reductase (ferredoxin) (EC 1.8.7.1, ferredoxin-sulfite reductase) is an enzyme with systematic name hydrogen-sulfide:ferredoxin oxidoreductase. This enzyme catalises the following chemical reaction
Sulfamethizole is a sulfonamide antibiotic.
The glycerol-3-phosphate shuttle is a mechanism used in skeletal muscle and the brain that regenerates NAD+ from NADH, a by-product of glycolysis. The NADH generated during glycolysis is found in the cytoplasm and must be transported into the mitochondria to enter the oxidative phosphorylation pathway. However, the inner mitochondrial membrane is impermeable to NADH and NAD+ and does not contain a transport system for these electron carriers. Either the glycerol-3-phosphate shuttle pathway or the malate-aspartate shuttle pathway, depending on the tissue of the organism, must be taken to transport electrons from cytoplasmic NADH into the mitochondria. The shuttle consists of the sequential activity of two proteins; Cytoplasmic glycerol-3-phosphate dehydrogenase (cGPD) transfers an electron pair from NADH to dihydroxyacetone phosphate (DHAP), forming glycerol-3-phosphate (G3P) and regenerating NAD+ needed to generate energy via glycolysis. The other protein, mitochondrial glycerol-3-phosphate dehydrogenase (mGPD) catalyzes the oxidation of G3P by FAD, regenerating DHAP in the cytosol and forming FADH2 in the mitochondrial matrix. In mammals, its activity in transporting reducing equivalents across the mitochondrial membrane is considered secondary to the malate-aspartate shuttle.
Nitrate reductase (NADPH) (EC 1.7.1.3, assimilatory nitrate reductase, assimilatory reduced nicotinamide adenine dinucleotide phosphate-nitrate reductase, NADPH-nitrate reductase, assimilatory NADPH-nitrate reductase, triphosphopyridine nucleotide-nitrate reductase, NADPH:nitrate reductase, nitrate reductase (NADPH2), NADPH2:nitrate oxidoreductase) is an enzyme with systematic name nitrite:NADP+ oxidoreductase. This enzyme catalises the following chemical reaction
Nitrate reductase (NAD(P)H) (EC 1.7.1.2, assimilatory nitrate reductase, assimilatory NAD(P)H-nitrate reductase, NAD(P)H bispecific nitrate reductase, nitrate reductase (reduced nicotinamide adenine dinucleotide (phosphate)), nitrate reductase NAD(P)H, NAD(P)H-nitrate reductase, nitrate reductase [NAD(P)H2], NAD(P)H2:nitrate oxidoreductase) is an enzyme with systematic name nitrite:NAD(P)+ oxidoreductase. This enzyme catalises the following chemical reaction
Nitrate reductase (NADH) (EC 1.7.1.1, assimilatory nitrate reductase, NADH-nitrate reductase, NADH-dependent nitrate reductase, assimilatory NADH: nitrate reductase, nitrate reductase (NADH2), NADH2: nitrate oxidoreductase) is an enzyme with systematic name nitrite: NAD+ oxidoreductase. This enzyme catalyzes the following chemical reaction
Mitochondrial uncoupling protein 2 is a protein that in humans is encoded by the UCP2 gene.
In enzymology, a glycolate dehydrogenase is an enzyme that catalyzes the chemical reaction
In enzymology, a formate dehydrogenase (cytochrome-c-553) (EC 1.2.2.3) is an enzyme that catalyzes the chemical reaction
Biochimica et Biophysica Acta (BBA) is a peer-reviewed scientific journal in the field of biochemistry and biophysics that was established in 1947. The journal is published by Elsevier with a total of 100 annual issues in ten specialised sections.
Tenuazonic acid is a mycotoxin produced by Alternaria species. It is a powerful eukaryotic protein synthesis inhibitor. It is a tetrameric acid that is ubiquitous in biological environments and prevents the release of newly synthesized protein from the ribosome. Its toxicity is the highest among all Alternaria mycotoxins and has both phytotoxic and cytotoxic properties. In 1991 Tenuazonic acid was reported to inhibit skin tumor promotion in mice.
An uncoupler or uncoupling agent is a molecule that disrupts oxidative phosphorylation in prokaryotes and mitochondria or photophosphorylation in chloroplasts and cyanobacteria by dissociating the reactions of ATP synthesis from the electron transport chain. The result is that the cell or mitochondrion expends energy to generate a proton-motive force, but the proton-motive force is dissipated before the ATP synthase can recapture this energy and use it to make ATP. Because the intracellular supply of protons is replenished, uncouplers actually stimulate cellular metabolism. Uncouplers are capable of transporting protons through mitochondrial and lipid membranes.
NADH dehydrogenase is an enzyme that converts nicotinamide adenine dinucleotide (NAD) from its reduced form (NADH) to its oxidized form (NAD+). Members of the NADH dehydrogenase family and analogues are commonly systematically named using the format NADH:acceptor oxidoreductase. The chemical reaction these enzymes catalyze is generally represented with the following equation:
Fluazinam is a broad-spectrum fungicide used in agriculture. It is classed as a diarylamine and more specifically an arylaminopyridine. Its chemical name is 3-chloro-N-(3-chloro-2,6-dinitro-4-trifluoromethylphenyl)-5-trifluoromethyl-2-pyridinamine. The mode of action involves the compound being an extremely potent uncoupler of oxidative phosphorylation in mitochondria and also having high reactivity with thiols. It is unique amongst uncouplers in displaying broad-spectrum activity against fungi and also very low toxicity to mammals due to it being rapidly metabolised to a compound without uncoupling activity. It was first described in 1992 and was developed by researchers at the Japanese company Ishihara Sangyo Kaisha.
Orange carotenoid protein (OCP) is a water-soluble protein which plays a role in photoprotection in diverse cyanobacteria. It is the only photoactive protein known to use a carotenoid as the photoresponsive chromophore. The protein consists of two domains, with a single keto-carotenoid molecule non-covalently bound between the two domains. It is a very efficient quencher of excitation energy absorbed by the primary light-harvesting antenna complexes of cyanobacteria, the phycobilisomes. The quenching is induced by blue-green light. It is also capable of preventing oxidative damage by directly scavenging singlet oxygen (1O2).
David W. Krogmann was an American biologist and a professor of biochemistry at Purdue University. He is known for his work in photosynthesis in chloroplasts and cyanobacteria.
