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The stoichiometry of cytochrome c to Apaf-1 within the complex is proved to be 1:1. [1] There are some debates about whether stable incorporation of cytochrome c into the apoptosome is required following oligomerization, but recent structural data favor the idea that cytochrome c stabilizes the oligomeric human apoptosome. [1]
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 ...
Upon binding cytochrome c and dATP, this protein forms an oligomeric apoptosome. The apoptosome binds and cleaves Procaspase-9 protein, releasing its mature, activated form. The precise mechanism for this reaction is still debated though work published by Guy Salvesen suggests that the apoptosome may induce caspase-9 dimerization and subsequent ...
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 ...
Depending on their function, once activated, Bcl-2 proteins either promote the release of these factors, or keep them sequestered in the mitochondria. Whereas the activated pro-apoptotic Bak and/or Bax would form MAC and mediate the release of cytochrome c, the anti-apoptotic Bcl-2 would block it, possibly through inhibition of Bax and/or Bak. [18]
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]
The pro-apoptotic proteins in the BCL-2 family, including Bax and Bak, normally act on the mitochondrial membrane to promote permeabilization and release of cytochrome c and ROS, that are important signals in the apoptosis cascade.
However, cytochrome c is only released if the mitochondrial membrane is compromised. Once cytochrome c is detected, the apoptosome complex is formed. This complex activates the executioner caspase which causes cell death. This killing of the cells may be essential as it prevents cellular overgrowth which can result in disease such as cancer ...