Surface thermodynamic properties of monolayers versus reconstitution of a membrane protein in solid-supported bilayers.
Atomic force microscopy (AFM) was used to study the influence of a membrane protein, lactose permease of Escherichia coli (LacY), on the surface spreading behavior and the features of self-assembled phospholipids bilayers on mica. The miscibility of phospholipids used, 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC), was investigated by surface pressure area isotherm measurements at the air-water interface. A composition with an equimolar proportion of POPC and DMPC was used to form the liposomes. Surface layers formed with DMPC:POPC (0.5:0.5, mol/mol) or LacY reconstituted in proteoliposomes with the same phospholipid composition were imaged by using AFM. When lactose permease was reconstituted in DMPC:POPC (0.5:0.5, mol/mol), self-assembled structures that remained firmly adsorbed onto the mica surface were observed. These sheets had an irregular shape and their upper layer was more corrugated than that obtained for the phospholipid matrix.
Merino
Sandra
S
Departament de Fisicoquímica, Facultat de Farmàcia, Universitat de Barcelona, 08028 Barcelona, Spain.
Domènech
Oscar
O
Díez-Pérez
Ismael
I
Sanz
Fausto
F
Montero
M Teresa
MT
Hernández-Borrell
Jordi
J
D000327:Adsorption; D000388:Air; D004134:Dimyristoylphosphatidylcholine / Q000737:chemistry; D004926:Escherichia coli / Q000378:metabolism; D006358:Hot Temperature; D008051:Lipid Bilayers / Q000737:chemistry*; D008081:Liposomes / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000378:metabolism; D018625:Microscopy, Atomic Force; D015233:Models, Statistical; D010713:Phosphatidylcholines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry; D011312:Pressure; D013499:Surface Properties; D013816:Thermodynamics; D014867:Water / Q000737:chemistry
D008051:Lipid Bilayers; D008081:Liposomes; D026901:Membrane Transport Proteins; D010713:Phosphatidylcholines; D010743:Phospholipids; D014867:Water; C021499:lactose permease; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D004134:Dimyristoylphosphatidylcholine