Unfolding and refolding of a protein by cholesterol and cyclodextrin: a single molecule study.
Phys Chem Chem Phys
; 17(12): 8017-27, 2015 Mar 28.
Article
em En
| MEDLINE
| ID: mdl-25721673
ABSTRACT
Unfolding/refolding of a plasma protein, human serum albumin (HSA), is studied using fluorescence correlation spectroscopy (FCS) and single molecule fluorescence resonance energy transfer (sm-FRET). Addition of cholesterol causes unfolding of HSA resulting in an increase in the hydrodynamic diameter (dH = 2rH) from 76 Å in the native state to 120 Å upon addition of 1 mM cholesterol. Addition of ß-cyclodextrin to HSA (unfolded by cholesterol) restores the hydrodynamic diameter back to 78 Å. The cholesterol induced unfolding and ß-cyclodextrin induced refolding are also monitored by measuring the distance between a FRET donor (CPM dye, D) and a FRET acceptor (Alexa 488, A) covalently attached to the protein (HSA). It is observed that the average D-A distance increases from 45 ± 1 Å at 0 mM cholesterol to 51 ± 1 Å at 1 mM cholesterol. Upon addition of ß-cyclodextrin, the D-A distance is restored to 45 ± 1 Å. The binding study indicates that nearly 94% of HSA molecules remain bound to cholesterol in the absence of ß-cyclodextrin and only 5% binds to cholesterol in the presence of ß-cyclodextrin. As much as 57% of the HSA and 99% of the cholesterol molecules bind to ß-cyclodextrin. Thus ß-cyclodextrin removes cholesterol from HSA by hydrophobic binding to cholesterol ("strip off") and also, itself binds to HSA. The conformational dynamics results suggest that addition of ß-cyclodextrin restores native like binding free energy and folding dynamics.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Albumina Sérica
/
Colesterol
/
Beta-Ciclodextrinas
Limite:
Humans
Idioma:
En
Revista:
Phys Chem Chem Phys
Assunto da revista:
BIOFISICA
/
QUIMICA
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Índia