The proapoptotic protein tBid forms both superficially bound and membrane-inserted oligomers.
Biophys J
; 106(10): 2085-95, 2014 May 20.
Article
en En
| MEDLINE
| ID: mdl-24853737
ABSTRACT
Bid is a proapopotic activator protein of the Bcl-2 family that plays a pivotal role in controlling mitochondrial outer membrane permeabilization during apoptosis. Here, we characterized the interaction of fluorescently labeled truncated Bid (tBid) with a mitochondria-like supported lipid bilayer at the single-molecule level. The proteins observed at the membrane exhibited a very wide range of mobility. Confocal images of the membrane displayed both diffraction-limited Gaussian spots and horizontal streaks, corresponding to immobile and mobile tBid species, respectively. We observed 1), fast-diffusing proteins corresponding to a loosely, probably electrostatically bound state; 2), slowly diffusing proteins, likely corresponding to a superficially inserted state; and 3), fully immobilized proteins, suggesting a fully inserted state. The stoichiometry of these proteins was determined by normalizing their fluorescence intensity by the brightness of a tBid monomer, measured separately using fluorescence fluctuation techniques. Strikingly, the immobile species were found to be mainly tetramers and higher, whereas the mobile species had on average a significantly lower stoichiometry. Taken together, these results show that as soluble Bid progresses toward a membrane-inserted state, it undergoes an oligomerization process similar to that observed for Bax.
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Membrana Celular
/
Apoptosis
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Proteína Proapoptótica que Interacciona Mediante Dominios BH3
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Multimerización de Proteína
Límite:
Animals
Idioma:
En
Revista:
Biophys J
Año:
2014
Tipo del documento:
Article
País de afiliación:
Canadá