In apoptosis, cytochrome C acts through -

Ans. is 'a' i.e., Apaf 1o One of these proteins is cytochrome c, well known for its role in mitochondrial respiration. In the cytosol, cytochrome C binds to a protein called Apaf-1 (apoptosis activating factor-1), and the complex activates caspase-9. (Bc1-2 and Bcl-x may also directly inhibit Apaf-1 activation, and their loss from cells may permit activation of Apaf-1).