Related Experiment Video
Updated: Aug 9, 2026

Isolation and Functional Analysis of Mitochondria from Cultured Cells and Mouse Tissue
Published on: March 23, 2015
Direct addition of BimL to mitochondria does not lead to cytochrome c release
Olivier Terradillos1, Sylvie Montessuit, David C S Huang
1Département de Biologie Cellulaire, Sciences III, 30 quai E. Ansermet, 1211 Genève 4, Switzerland.
Abstract:
Pro-apoptotic members of the Bcl-2 family can be subdivided in two classes according to their structure: a group including Bax, Bak, and Bok that display Bcl-2 homology (BH) 1, BH2 and BH3 domains and a second group including Bid (BH3 interacting domain death agonist), Bad, Bim (Bcl-2 interacting mediator of cell death) and several others that contain only a BH3 domain, the BH3-only proteins. The BH3-only proteins have been proposed to activate pro-apoptotic members of the Bax subfamily to trigger a mitochondrial pathway that leads to the release of cytochrome c and other apoptogenic factors. Here we report that the mechanism of action of Bim is different from that of Bid. Although overexpression of Bid or Bim in cells leads to cytochrome c release, only Bid is able to trigger the release of cytochrome c through Bax activation when added directly to isolated mitochondria. Bim(L), although unable to activate Bax, can directly inhibit Bcl-2 or Bcl-x(L). Our data suggest two functional classes of BH3-only proteins: those such as Bid which directly activate Bax-like proteins leading to mitochondrial membrane permeability and apoptosis and those such as Bim which inhibit anti-apoptotic proteins and render the cells more susceptible to apoptogenic stimuli.
Related Concept Videos
Pyruvate Oxidation
First, the enzyme pyruvate dehydrogenase removes the carboxyl group from pyruvate and releases it as carbon dioxide. The stripped molecule is then oxidized and releases electrons, which are then picked up by NAD+...
Mitochondria
Mitochondrial Membranes
Mitochondrial Protein Sorting
Most of these mitochondrial proteins are encoded by the nucleus and imported to the mitochondria as unfolded or loosely folded precursors. Mitochondrial precursors...
Translocation of Proteins into the Mitochondria
Sorting of outer membrane proteins:
Mitochondrial outer membrane proteins are of two types: the transmembrane, beta-barrel porins, and the membrane-anchored, alpha-helical proteins. Beta-barrel porin precursors are translocated by the TOM complex and inserted into the outer mitochondrial membrane by the SAM complex. In contrast,...
Porin Insertion in the Outer Mitochondrial Membrane
Three models describe the assembly of porins by the SAM complex and their insertion into the outer membrane. Model 1 suggests that porins are assembled outside the SAM channel as the...

