Figure 5.

In the absence of cytosol, Bid and Bax release cytochrome c and adenylate kinase, but do not develop high complex IV accessibility. Xenopus egg mitochondria were incubated in buffer B or cytosol alone, or with added tBid (170 ng/ml) or Bax (37 μg/ml) for 4 h at 22°C. At the indicated times, aliquots were measured for (A) mitochondrial cytochrome c content, (B) mitochondrial adenylate kinase activity, and (C) complex IV accessibility. Data are single measurements except those for adenylate kinase (mean and SD of triplicates), and are representative of two experiments. (D) PEF acts subsequent to tBid, and tBid effects on the outer membrane are sustained. Xenopus mitochondria were first incubated at 22°C in buffer B with or without tBid (170 ng/ml) for 2 h to allow tBid to cause complete cytochrome c release (not shown). Mitochondria were then washed in buffer B and resuspended in fresh cytosol, and aliquots were tested every 15 min for complex IV accessibility.