Succinate dehydrogenase (SDH) or succinate-coenzyme Q reductase (SQR) or respiratory complex II is an enzyme complex, found in many bacterial cells and in the inner mitochondrial membrane of eukaryotes. It is the only enzyme that participates in both the citric acid cycle and the electron transport chain. Histochemical analysis showing high succinate dehydrogenase in muscle demonstrates high mitochondrial content and high oxidative potential.
Succinate dehydrogenase [ubiquinone] cytochrome b small subunit, mitochondrial (CybS), also known as succinate dehydrogenase complex subunit D (SDHD), is a protein that in humans is encoded by the SDHD gene. Names previously used for SDHD were PGL and PGL1. Succinate dehydrogenase is an important enzyme in both the citric acid cycle and the electron transport chain. Hereditary PGL-PCC syndrome is caused by a parental imprint of the SDHD gene. Screening can begin by 6 years of age.
Succinate dehydrogenase complex subunit C, also known as succinate dehydrogenase cytochrome b560 subunit, mitochondrial, is a protein that in humans is encoded by the SDHC gene. This gene encodes one of four nuclear-encoded subunits that comprise succinate dehydrogenase, also known as mitochondrial complex II, a key enzyme complex of the tricarboxylic acid cycle and aerobic respiratory chains of mitochondria. The encoded protein is one of two integral membrane proteins that anchor other subunits of the complex, which form the catalytic core, to the inner mitochondrial membrane. There are several related pseudogenes for this gene on different chromosomes. Mutations in this gene have been associated with pheochromocytomas and paragangliomas. Alternatively spliced transcript variants have been described.
Succinate dehydrogenase [ubiquinone] iron-sulfur subunit, mitochondrial (SDHB) also known as iron-sulfur subunit of complex II (Ip) is a protein that in humans is encoded by the SDHB gene.
Succinate dehydrogenase complex, subunit A, flavoprotein variant is a protein that in humans is encoded by the SDHA gene. This gene encodes a major catalytic subunit of succinate-ubiquinone oxidoreductase, a complex of the mitochondrial respiratory chain. The complex is composed of four nuclear-encoded subunits and is localized in the mitochondrial inner membrane. SDHA contains the FAD binding site where succinate is deprotonated and converted to fumarate. Mutations in this gene have been associated with a form of mitochondrial respiratory chain deficiency known as Leigh Syndrome. A pseudogene has been identified on chromosome 3q29. Alternatively spliced transcript variants encoding different isoforms have been found for this gene.
MT-ND5 is a gene of the mitochondrial genome coding for the NADH-ubiquinone oxidoreductase chain 5 protein (ND5). The ND5 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Variations in human MT-ND5 are associated with mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes (MELAS) as well as some symptoms of Leigh's syndrome and Leber's hereditary optic neuropathy (LHON).
NADH dehydrogenase [ubiquinone] iron-sulfur protein 4, mitochondrial (NDUFS4) also known as NADH-ubiquinone oxidoreductase 18 kDa subunit is an enzyme that in humans is encoded by the NDUFS4 gene. This gene encodes a nuclear-encoded accessory subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase. Complex I removes electrons from NADH and passes them to the electron acceptor ubiquinone. Mutations in this gene can cause mitochondrial complex I deficiencies such as Leigh syndrome.
NADH dehydrogenase [ubiquinone] flavoprotein 1, mitochondrial (NDUFV1) is an enzyme that in humans is encoded by the NDUFV1 gene. The NDUFV1 gene encodes the 51-kD subunit of complex I of the mitochondrial respiratory chain. Defects in complex I are a common cause of mitochondrial dysfunction. Mitochondrial complex I deficiency is linked to myopathies, encephalomyopathies, and neurodegenerative disorders such as Parkinson's disease and Leigh syndrome.
NADH dehydrogenase [ubiquinone] iron-sulfur protein 2, mitochondrial (NDUFS2) also known as NADH-ubiquinone oxidoreductase 49 kDa subunit is an enzyme that in humans is encoded by the NDUFS2 gene. The protein encoded by this gene is a core subunit of the mitochondrial membrane respiratory chain NADH dehydrogenase. Mutations in this gene are associated with mitochondrial complex I deficiency.
NADH dehydrogenase [ubiquinone] 1 alpha subcomplex subunit 1 is a protein that in humans is encoded by the NDUFA1 gene. The NDUFA1 protein is a subunit of NADH dehydrogenase (ubiquinone), which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Mutations in the NDUFA1 gene are associated with mitochondrial Complex I deficiency.
NADH-ubiquinone oxidoreductase 75 kDa subunit, mitochondrial (NDUFS1) is an enzyme that in humans is encoded by the NDUFS1 gene. The encoded protein, NDUFS1, is the largest subunit of complex I, located on the inner mitochondrial membrane, and is important for mitochondrial oxidative phosphorylation. Mutations in this gene are associated with complex I deficiency.
Cytochrome b-c1 complex subunit 2, mitochondrial (UQCRC2), also known as QCR2, UQCR2, or MC3DN5 is a protein that in humans is encoded by the UQCRC2 gene. The product of UQCRC2 is a subunit of the respiratory chain protein Ubiquinol Cytochrome c Reductase, which consists of the products of one mitochondrially encoded gene, MTCYTB and ten nuclear genes: UQCRC1, UQCRC2, Cytochrome c1, UQCRFS1, UQCRB, "11kDa protein", UQCRH, Rieske Protein presequence, "cyt. c1 associated protein", and "Rieske-associated protein." Defects in UQCRC2 are associated with mitochondrial complex III deficiency, nuclear, type 5.
Iron-sulfur cluster assembly enzyme ISCU, mitochondrial is a protein that in humans is encoded by the ISCU gene. It encodes an iron-sulfur (Fe-S) cluster scaffold protein involved in [2Fe-2S] and [4Fe-4S] cluster synthesis and maturation. A deficiency of ISCU is associated with a mitochondrial myopathy with lifelong exercise intolerance where only minor exertion causes tachycardia, shortness of breath, muscle weakness and myalgia.
NADH dehydrogenase [ubiquinone] 1 alpha subcomplex assembly factor 3, also known as 2P1, E3-3, or C3orf60, is a protein that in humans is encoded by the NDUFAF3 gene. NDUFAF3 is a mitochondrial assembly protein involved in the assembly of NADH dehydrogenase (ubiquinone) also known as complex I, which is located in the mitochondrial inner membrane and is the largest of the five complexes of the electron transport chain. Mutations in this gene have been associated with severe complex I deficiency and Leigh syndrome.
NADH dehydrogenase [ubiquinone] 1 beta subcomplex subunit 11, mitochondrial is an enzyme that in humans is encoded by the NDUFB11 gene. NADH dehydrogenase (ubiquinone) 1 beta subcomplex subunit 11 is an accessory subunit of the NADH dehydrogenase (ubiquinone) complex, located in the mitochondrial inner membrane. It is also known as Complex I and is the largest of the five complexes of the electron transport chain. NDUFB11 mutations have been associated with linear skin defects with multiple congenital anomalies 3 and mitochondrial complex I deficiency.
Succinate dehydrogenase complex assembly factor 2, formerly known as SDH5 and also known as SDH assembly factor 2 or SDHAF2 is a protein that in humans is encoded by the SDHAF2 gene. This gene encodes a mitochondrial protein needed for the flavination of a succinate dehydrogenase complex subunit required for activity of the complex. Mutations in this gene are associated with pheochromocytoma and paraganglioma.
NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 3, 12kDa is a protein that in humans is encoded by the NDUFB3 gene. NADH dehydrogenase (ubiquinone) 1 beta subcomplex, 3, 12kDa is an accessory subunit of the NADH dehydrogenase (ubiquinone) complex, located in the mitochondrial inner membrane. It is also known as Complex I and is the largest of the five complexes of the electron transport chain. Mutations in this gene contribute to mitochondrial complex I deficiency.
NADH:ubiquinone oxidoreductase complex assembly factor 6 is a protein that in humans is encoded by the NDUFAF6 gene. The protein is involved in the assembly of complex I in the mitochondrial electron transport chain. Mutations in the NDUFAF6 gene have been shown to cause Complex I deficiency, Leigh syndrome, and Acadian variant Fanconi Syndrome.
LYR motif containing 7, also known as Complex III assembly factor LYRM7 or LYR motif-containing protein 7 is a protein that in humans is encoded by the LYRM7 gene. The protein encoded by this gene is a nuclear-encoded mitochondrial matrix protein that stabilizes UQCRFS1 and chaperones it to the CIII complex. Defects in this gene are a cause of mitochondrial complex III deficiency, nuclear type 8. Three transcript variants encoding two different isoforms have been found for this gene.
Cytochrome c oxidase assembly factor 5 is a protein that in humans is encoded by the COA5 gene. This gene encodes an ortholog of yeast Pet191, which in yeast is a subunit of a large oligomeric complex associated with the mitochondrial inner membrane, and required for the assembly of the cytochrome c oxidase complex. Mutations in this gene are associated with mitochondrial complex IV deficiency.
