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Cytochrome b is a protein found in the membranes of aerobic cells. In eukaryotic mitochondria (inner membrane) and in aerobic prokaryotes , cytochrome b is a component of respiratory chain complex III ( EC 1.10.2.2 ) — also known as the bc1 complex or ubiquinol-cytochrome c reductase.
Location of the MT-CYB gene in the human mitochondrial genome (coral box).. Cytochrome b is a protein that in humans is encoded by the MT-CYB gene. [5] Its gene product is a subunit of the respiratory chain protein ubiquinol–cytochrome c reductase (UQCR, complex III or cytochrome bc 1 complex), which consists of the products of one mitochondrially encoded gene, MT-CYB (mitochondrial ...
Complex IV contains a cytochrome a/a3-domain that transfers electrons and catalyzes the reaction of oxygen to water. Photosystem II, the first protein complex in the light-dependent reactions of oxygenic photosynthesis, contains a cytochrome b subunit. Cyclooxygenase 2, an enzyme involved in inflammation, is a cytochrome b protein.
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
Moreover, nuclear DNA genes involved in aerobic respiration and in mitochondrial DNA replication and transcription were either absent or present only as pseudogenes. This is the first multicellular organism known to have this absence of aerobic respiration and live completely free of oxygen dependency. [20] [21]
The major enzymatic functions carried out at the replication fork are well conserved from prokaryotes to eukaryotes, but the replication machinery in eukaryotic DNA replication is a much larger complex, coordinating many proteins at the site of replication, forming the replisome.
In humans, mitochondrial DNA (mtDNA) forms closed circular molecules that contain 16,569 [4] [5] DNA base pairs, [6] with each such molecule normally containing a full set of the mitochondrial genes. Each human mitochondrion contains, on average, approximately 5 such mtDNA molecules, with the quantity ranging between 1 and 15. [ 6 ]
NUMT insertion into the nuclear genome and its persistence in the nuclear genome is initiated by the physical delivery of mitochondrial DNA to the nucleus. [5] This step follows by the mtDNA integration into the genome through a non-homologous end joining mechanism during the double-strand break (DSB) repair process as envisioned by studying Saccharomyces cerevisiae, [13] [29] and terminates ...