Solution structure of human BCL-w: modulation of ligand binding by the C-terminal helix.
The structure of human BCL-w, an anti-apoptotic member of the BCL-2 family, was determined by triple-resonance NMR spectroscopy and molecular modeling. Introduction of a single amino acid substitution (P117V) significantly improved the quality of the NMR spectra obtained. The cytosolic domain of BCL-w consists of 8 alpha-helices, which adopt a fold similar to that of BCL-xL, BCL-2, and BAX proteins. Pairwise root meant square deviation values were less than 3 A for backbone atoms of structurally equivalent regions. Interestingly, the C-terminal helix alpha8 of BCL-w folds into the BH3-binding hydrophobic cleft of the protein, in a fashion similar to the C-terminal transmembrane helix of BAX. A peptide corresponding to the BH3 region of the pro-apoptotic protein, BID, could displace helix alpha8 from the BCL-w cleft, resulting in helix unfolding. Deletion of helix alpha8 increased binding affinities of BCL-w for BAK and BID BH3-peptides, indicating that this helix competes for peptide binding to the hydrophobic cleft. These results suggest that although the cytosolic domain of BCL-w exhibits an overall structure similar to that of BCL-xL and BCL-2, the unique organization of its C-terminal helix may modulate BCL-w interactions with pro-apoptotic binding partners.
Denisov
Alexei Yu
AY
Department of Biochemistry and Montreal Joint Center for Structural Biology, McGill University, Montreal, Quebec H3G 1Y6, Canada.
Madiraju
Murthy S R
MS
Chen
Gang
G
Khadir
Abdelkrim
A
Beauparlant
Pierre
P
Attardo
Giorgio
G
Shore
Gordon C
GC
Gehring
Kalle
K
D000595:Amino Acid Sequence; D051017:Apoptosis Regulatory Proteins; D003600:Cytosol; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011506:Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D051020:bcl-X Protein
D051017:Apoptosis Regulatory Proteins; C494811:BCL2L1 protein, human; C491073:BCL2L2 protein, human; D008024:Ligands; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein