Investigation of the role of the C-terminus of Bax and of tc-Bid on Bax interaction with yeast mitochondria.
Because of structural homology with the transmembrane domain of Bcl-2, the proapoptotic protein Bax has been proposed to be anchored to the outer membrane of mitochondria through its carboxy-terminal end (CT). We took advantage of the absence of Bcl-2 family members in yeast to further investigate the role of Bax CT in its mitochondrial association and function. The complete deletion or the addition of a C-terminal c-myc tag as well as the replacement of CT by a random coiled sequence enhanced membrane insertion of Bax. It has previously been suggested that conformational change in the N-terminal end of Bax would allow the C-terminal end to play its anchoring function. We found that a mutant truncated in both N- and C-termini still exhibited a strong binding activity to mitochondria. In mammals, Bax interaction with the caspase-8-generated truncated form of Bid (tc-Bid) is believed to promote a conformational change necessary for the insertion of Bax into mitochondria. We coexpressed Bax and tc-Bid in yeast and found that native Bax functions are not stimulated by tc-Bid, whereas functions of an active variant with a modified CT are. We propose that Bax CT has to undergo a conformational change to allow the insertion of Bax in mitochondria but, contrary to current views, is not a bona fide membrane anchor.
Priault
Muriel
M
UMR 5095 CNRS/Université de Bordeaux 2, 1 Rue Camille Saint-Saëns, F-33077 Bordeaux, France.
Cartron
Pierre-François
PF
Camougrand
Nadine
N
Antonsson
Bruno
B
Vallette
François M
FM
Manon
Stéphen
S
D000595:Amino Acid Sequence; D000818:Animals; D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins / Q000032:analysis / Q000737:chemistry / Q000502:physiology*; D016923:Cell Death; D008928:Mitochondria / Q000378:metabolism*; D024101:Mitochondrial Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D011487:Protein Conformation; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics; D011993:Recombinant Fusion Proteins / Q000032:analysis / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D015003:Yeasts / Q000166:cytology / Q000378:metabolism; D051028:bcl-2-Associated X Protein
D051023:BH3 Interacting Domain Death Agonist Protein; D002352:Carrier Proteins; D024101:Mitochondrial Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D016271:Proto-Oncogene Proteins c-myc; D011993:Recombinant Fusion Proteins; D051028:bcl-2-Associated X Protein