title: Oligomeric C-terminal truncated Bax preferentially releases cytochrome c but not adenylate kinase from mitochondria, outer membrane vesicles and proteoliposomes.
abstract: The mechanism by which the proapoptotic protein Bax releases cytochrome c from mitochondria is not fully understood. The present work approaches this problem using C-terminal truncated oligomeric Bax (BaxDeltaC). Micromolar concentrations of BaxDeltaC released cytochrome c from isolated rat heart and liver mitochondria, while the release of adenylate kinase was not significantly affected. BaxDeltaC also released cytochrome c but not adenylate kinase from outer membrane vesicles filled with these proteins. However, BaxDeltaC was ineffective in releasing cytochrome c when outer membrane vesicles were obtained in the presence of glycerol, conditions under which the number of contact sites was drastically reduced. BaxDeltaC did not liberate encapsulated cytochrome c and adenylate kinase from pure phospholipid vesicles or vesicles reconstituted with porin. However, when the hexokinase-porin-adenine nucleotide translocase complex from brain mitochondria was reconstituted in vesicles, BaxDeltaC released internal cytochrome c but not adenylate kinase. In all these systems, only a small portion of total cytochrome c present in either mitochondria or vesicles could be liberated by BaxDeltaC. BaxDeltaC also increased the accessibility of external cytochrome c to either oxidation by complex IV or reduction by complex III in intact liver and heart mitochondria.
  
  
  CONCLUSIONS
  (1) BaxDeltaC selectively releases cytochrome c and enables a bidirectional movement of cytochrome c across the outer mitochondrial membrane. (2) A multiprotein complex that resembles the mitochondrial contact sites is a prerequisite for BaxDeltaC action. (3) A limited pool of cytochrome c becomes the first target for BaxDeltaC.
authors.affiliation: Nencki Institute of Experimental Biology, Warsaw, Poland.
authors.forename: M R
authors.initials: MR
authors.lastname: Wieckowski
authors.forename: M
authors.initials: M
authors.lastname: Vyssokikh
authors.forename: D
authors.initials: D
authors.lastname: Dymkowska
authors.forename: B
authors.initials: B
authors.lastname: Antonsson
authors.forename: D
authors.initials: D
authors.lastname: Brdiczka
authors.forename: L
authors.initials: L
authors.lastname: Wojtczak
mesh_terms: D000263:Adenylate Kinase / Q000378:metabolism*; D000818:Animals; D001704:Biopolymers; D002462:Cell Membrane / Q000201:enzymology; D003574:Cytochrome c Group / Q000378:metabolism*; D008297:Male; D008929:Mitochondria, Heart / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000201:enzymology*; D046912:Multiprotein Complexes; D011510:Proteolipids; D011518:Proto-Oncogene Proteins / Q000737:chemistry / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D017208:Rats, Wistar; D051028:bcl-2-Associated X Protein
chemical_list: C494828:Bax protein, rat; D001704:Biopolymers; D003574:Cytochrome c Group; D046912:Multiprotein Complexes; D011510:Proteolipids; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C020485:proteoliposomes; D000263:Adenylate Kinase