Structural basis of BFL-1 for its interaction with BAX and its anti-apoptotic action in mammalian and yeast cells.
BFL-1 is the smallest member of the BCL-2 family and has been shown to retard apoptosis in various cell lines. However, the structural basis for its function remains unclear. Molecular modeling showed that BFL-1 could have a similar core structure as BCL-xL, consisting of seven alpha helices, although both proteins share only the conserved BCL-2 homology domains (BH1 and BH2 domains), but otherwise have very limited sequence homology, particularly in the N-terminal region. We demonstrated in the yeast two-hybrid system that BFL-1 interacts strongly with human BAX but is not able to form homodimers nor to interact with human BCL-2 or BCL-xL. Overexpression experiments in REF52 rat fibroblasts showed that BFL-1 conferred increased resistance to apoptosis induced by serum deprivation. BFL-1 had also the ability to neutralize BAX lethality in yeast. BAX requires the BH3 domain for interaction with BFL-1. However, the minimal region of BFL-1 for the interaction with BAX in coimmunoprecipitation experiments was not sufficient to protect cells from apoptosis. Further examination of BFL-1 and several other anti-apoptotic proteins suggests a more general type of structure based on structural motifs, i.e. a hydrophobic pocket for the binding of proapoptotic proteins, rather than extended sequence homologies.
Zhang
H
H
Novartis Pharma AG, Oncology, Molecular Genetics, CH-4002 Basel, Switzerland.
Cowan-Jacob
S W
SW
Simonen
M
M
Greenhalf
W
W
Heim
J
J
Meyhack
B
B
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001483:Base Sequence; D001665:Binding Sites; D016923:Cell Death; D002460:Cell Line; D006801:Humans; D015778:Minor Histocompatibility Antigens; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011506:Proteins / Q000737:chemistry* / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2; D051381:Rats; D012441:Saccharomyces cerevisiae / Q000502:physiology; D051028:bcl-2-Associated X Protein
C494826:BAX protein, human; C096816:BCL2-related protein A1; C494828:Bax protein, rat; D015778:Minor Histocompatibility Antigens; D011506:Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein