Assembly of Bcl-2 into microsomal and outer mitochondrial membranes.
Bcl-2 is thought to associate spontaneously with membranes via a carboxyl-terminal hydrophobic domain by a mechanism analogous to that of cytochrome b5. We have examined the association of Bcl-2 with a variety of highly purified intracellular membranes in vitro. Fusion proteins were used to assess directly the role of the carboxyl-terminal hydrophobic domain of Bcl-2 in membrane association. Although this domain of Bcl-2 was sufficient to promote the association of a normally cytosolic polypeptide with either microsomal or mitochondrial membranes additional nonhydrophobic amino-terminal residues were required for membrane integration. Furthermore, direct comparison of membrane binding of Bcl-2 and cytochrome b5 revealed that similar to cytochrome b5, membrane targeting of Bcl-2 was not dependent on protease-sensitive components of the recipient membranes. In competition experiments, cytochrome b5 demonstrated the expected preference for integration into endoplasmic reticulum membranes. In contrast, the data presented here suggest that Bcl-2 is targeted to the cytoplasmic surface of multiple intracellular membranes, both in vitro and in human leukemic cells.
Janiak
F
F
Department of Biochemistry, McMaster University, Hamilton, Ontario, Canada.
Leber
B
B
Andrews
D W
DW
D000818:Animals; D000831:Animals, Newborn; D015786:Cytochromes b5 / Q000096:biosynthesis* / Q000302:isolation & purification; D004285:Dogs; D007425:Intracellular Membranes / Q000378:metabolism*; D008081:Liposomes; D008565:Membrane Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D008861:Microsomes / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000378:metabolism*; D008930:Mitochondria, Liver / Q000378:metabolism*; D010179:Pancreas / Q000378:metabolism; D014176:Protein Biosynthesis; D011505:Protein-Tyrosine Kinases / Q000096:biosynthesis; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis* / Q000302:isolation & purification; D019253:Proto-Oncogene Proteins c-bcl-2; D011519:Proto-Oncogenes; D051381:Rats; D017207:Rats, Sprague-Dawley; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000302:isolation & purification; D013367:Submitochondrial Particles / Q000378:metabolism
D008081:Liposomes; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D011993:Recombinant Fusion Proteins; D015786:Cytochromes b5; D011505:Protein-Tyrosine Kinases