Identification of a novel regulatory domain in Bcl-X(L) and Bcl-2.
Bcl-X(L), a member of the Bcl-2 family, can inhibit many forms of programed cell death. The three-dimensional structure of Bcl-X(L) identified a 60 amino acid loop lacking defined structure. Although amino acid sequence within this region is not conserved among Bcl-2 family members, structural modeling suggested that Bcl-2 also contains a large unstructured region. Compared with the full-length protein, loop deletion mutants of Bcl-X(L) and Bcl-2 displayed an enhanced ability to inhibit apoptosis. Despite enhanced function, the deletion mutants did not have significant alterations in the ability to bind pro-apoptotic proteins such as Bax. The loop deletion mutant of Bcl-2 also displayed a qualitative difference in its ability to inhibit apoptosis. Full-length Bcl-2 was unable to prevent anti-IgM-induced cell death of the immature B cell line WEHI-231. In contrast, the Bcl-2 deletion mutant protected WEHI-231 cells from death. Substantial differences were observed in the ability of WEHI-231 cells to phosphorylate the deletion mutant of Bcl-2 compared with full-length Bcl-2. Bcl-2 phosphorylation was found to be dependent on the presence of an intact loop domain. These results suggest that the loop domain in Bcl-X(L) and Bcl-2 can suppress the anti-apoptotic function of these genes and may be a target for regulatory post-translational modifications.
Chang
B S
BS
Department of Medicine, The University of Chicago, IL 60637, USA.
Minn
A J
AJ
Muchmore
S W
SW
Fesik
S W
SW
Thompson
C B
CB
D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D001402:B-Lymphocytes / Q000166:cytology; D015153:Blotting, Western; D002470:Cell Survival; D002478:Cells, Cultured; D002999:Clone Cells; D019281:Dimerization; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D010766:Phosphorylation; D011233:Precipitin Tests; D011518:Proto-Oncogene Proteins / Q000737:chemistry* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry* / Q000378:metabolism; D017384:Sequence Deletion; D017386:Sequence Homology, Amino Acid; D014162:Transfection; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein
C494826:BAX protein, human; C494811:BCL2L1 protein, human; C494827:Bax protein, mouse; C494812:Bcl2l1 protein, mouse; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein