Unspecific membrane protein-lipid recognition: combination of AFM imaging, force spectroscopy, DSC and FRET measurements.
J Mol Recognit
; 28(11): 679-86, 2015 Nov.
Article
em En
| MEDLINE
| ID: mdl-26046777
ABSTRACT
In this work, we will describe in quantitative terms the unspecific recognition between lactose permease (LacY) of Escherichia coli, a polytopic model membrane protein, and one of the main components of the inner membrane of this bacterium. Supported lipid bilayers of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoglycerol (POPG) (31, mol/mol) in the presence of Ca(2+) display lateral phase segregation that can be distinguished by atomic force microscopy (AFM) as well as force spectroscopy. LacY shows preference for fluid (Lα) phases when it is reconstituted in POPE POPG (31, mol/mol) proteoliposomes at a lipid-to-protein ratio of 40. When the lipid-to-protein ratio is decreased down to 0.5, two domains can be distinguished by AFM. While the upper domain is formed by self-segregated units of LacY, the lower domain is constituted only by phospholipids in gel (Lß) phase. On the one hand, classical differential scanning calorimetry (DSC) measurements evidenced the segregation of a population of phospholipids and point to the existence of a boundary region at the lipid-protein interface. On the other hand, Förster Resonance Energy Transfer (FRET) measurements in solution evidenced that POPE is selectively recognized by LacY. A binary pseudophase diagram of POPE POPG built from AFM observations enables to calculate the composition of the fluid phase where LacY is inserted. These results are consistent with a model where POPE constitutes the main component of the lipid-LacY interface segregated from the fluid bulk phase where POPG predominates.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas de Bactérias
/
Bicamadas Lipídicas
/
Proteínas de Membrana
Idioma:
En
Revista:
J Mol Recognit
Assunto da revista:
BIOLOGIA MOLECULAR
Ano de publicação:
2015
Tipo de documento:
Article
País de afiliação:
Espanha