Conformation of membrane-associated proapoptotic tBid. J Biol Chem 2004 Jul 09;279(28):28954-60
Date
05/05/2004Pubmed ID
15123718Pubmed Central ID
PMC3033194DOI
10.1074/jbc.M403490200Scopus ID
2-s2.0-3142713275 (requires institutional sign-in at Scopus site) 59 CitationsAbstract
The proapoptotic Bcl-2 family protein Bid is cleaved by caspase-8 to release the C-terminal fragment tBid, which translocates to the outer mitochondrial membrane and induces massive cytochrome c release and cell death. In this study, we have characterized the conformation of tBid in lipid membrane environments, using NMR and CD spectroscopy with lipid micelle and lipid bilayer samples. In micelles, tBid adopts a unique helical conformation, and the solution NMR (1)H/(15)N HSQC spectra have a single well resolved resonance for each of the protein amide sites. In lipid bilayers, tBid associates with the membrane with its helices parallel to the membrane surface and without trans-membrane helix insertion, and the solid-state NMR (1)H/(15)N polarization inversion with spin exchange at the magic angle spectrum has all of the amide resonances centered at (15)N chemical shift (70-90 ppm) and (1)H-(15)N dipolar coupling (0-5 kHz) frequencies associated with NH bonds parallel to the bilayer surface, with no intensity at frequencies associated with NH bonds in trans-membrane helices. Thus, the cytotoxic activity of tBid at mitochondria may be similar to that observed for antibiotic polypeptides, which bind to the surface of bacterial membranes as amphipathic helices and destabilize the bilayer structure, promoting the leakage of cell contents.
Author List
Gong XM, Choi J, Franzin CM, Zhai D, Reed JC, Marassi FMAuthor
Francesca M. Marassi PhD Chair, Professor in the Biophysics department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
Amino Acid SequenceApoptosis
BH3 Interacting Domain Death Agonist Protein
Carrier Proteins
Cell Line
Cell Membrane
Circular Dichroism
Humans
Lipid Bilayers
Micelles
Mitochondria
Molecular Sequence Data
Nuclear Magnetic Resonance, Biomolecular
Peptide Fragments
Protein Conformation
Protein Folding
Proto-Oncogene Proteins c-bcl-2
bcl-X Protein
