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Cytochrome c is a highly conserved protein across the spectrum of eukaryotic species, found in plants, animals, fungi, and many unicellular organisms. This, along with its small size (molecular weight about 12,000 daltons), [7] makes it useful in studies of cladistics. [8] Cytochrome c has been studied for the glimpse it gives into evolutionary ...
In mammalian cells, once cytochrome c is released, it binds to the cytosolic protein Apaf-1 to facilitate the formation of an apoptosome. An early biochemical study suggests a two-to-one ratio of cytochrome c to apaf-1 for apoptosome formation. However, recent structural studies suggest the cytochrome c to apaf-1 ratio is one-to-one.
The X-linked inhibitor of apoptosis protein is overexpressed in cells of the H460 cell line. XIAPs bind to the processed form of caspase-9 and suppress the activity of apoptotic activator cytochrome c, therefore overexpression leads to a decrease in the number of proapoptotic agonists. As a consequence, the balance of anti-apoptotic and ...
Caspase-9 belongs to a family of caspases, cysteine-aspartic proteases involved in apoptosis and cytokine signalling. [8] Apoptotic signals cause the release of cytochrome c from mitochondria and activation of apaf-1 , which then cleaves the pro-enzyme of caspase-9 into the active dimer form. [6]
Within the mitochondria are apoptogenic factors (cytochrome c, Smac/Diablo homolog, Omi) that if released activate the executioners of apoptosis, the caspases. [17] Depending on their function, once activated, Bcl-2 proteins either promote the release of these factors, or keep them sequestered in the mitochondria.
Small soluble cytochrome c proteins with a molecular weight of 8-12 kDa and a single heme group belong to class I. [10] [11] It includes the low-spin soluble cytC of mitochondria and bacteria, with the heme-attachment site located towards the N-terminus, and the sixth ligand provided by a methionine residue about 40 residues further on towards the C-terminus.
There is no "cytochrome e," but cytochrome f, found in the cytochrome b 6 f complex of plants is a c-type cytochrome. [12] In mitochondria and chloroplasts, these cytochromes are often combined in electron transport and related metabolic pathways: [13]
This may be an important reason why cytochrome c is nearly ubiquitous throughout life. Heme C also plays an important role in apoptosis where just a few molecules of cytoplasmic cytochrome c, which must still contain heme C, leads to programmed cell death. [6] Cytochrome c can be measured in human serum and can be used as a marker for ...