Physical properties of liposomes and proteoliposomes prepared from Escherichia coli polar lipids

• Published in: Biochimica et biophysica acta Vol. 1468; no. 1; pp. 175 - 186
• Main Authors: White, Gisèle F, Racher, Kathleen I, Lipski, André, Hallett, F.Ross, Wood, Janet M
• Format: Journal Article
• Language: English
• Published: Netherlands Elsevier B.V 29.09.2000
• Subjects: Buffers; Calorimetry, Differential Scanning; Differential scanning calorimetry; Escherichia coli; Escherichia coli - chemistry; Escherichia coli - genetics; Fatty Acids - analysis; Hydrogen-Ion Concentration; Light; Light scattering; Lipid; Liposome; Liposomes - chemistry; Melting transition; Membrane; Membrane protein; Osmolar Concentration; Particle Size; Phospholipid; Proteolipids - chemistry; Proteoliposome; Scattering, Radiation; Sodium Chloride; Sucrose; Differential scanning calorimetry; Proteoliposome; Membrane protein; Light scattering; Escherichia coli; Liposome; Melting transition; Phospholipid; Membrane; Lipid
• ISSN: 0005-2736; 0006-3002; 1879-2642
• DOI: 10.1016/S0005-2736(00)00255-8

Reconstituted proteoliposomes serve as experimental systems for the study of membrane enzymes. Osmotic shifts and other changes in the solution environment may influence the structures and membrane properties of phospholipid vesicles (including liposomes, proteoliposomes and biological membrane vesicles) and hence the activities of membrane-associated proteins. Polar lipid extracts from Escherichia coli are commonly used in membrane protein reconstitution. The solution environment influenced the phase transition temperature and the diameter of liposomes and proteoliposomes prepared from E. coli polar lipid by extrusion. Liposomes prepared from E. coli polar lipids differed from dioleoylphosphatidylglycerol liposomes in Young’s elastic modulus, yield point for solute leakage and structural response to osmotic shifts, the latter indicated by static light scattering spectroscopy. At high concentrations, NaCl caused aggregation of E. coli lipid liposomes that precluded detailed interpretation of light scattering data. Proteoliposomes and liposomes prepared from E. coli polar lipids were similar in size, yield point for solute leakage and structural response to osmotic shifts imposed with sucrose as osmolyte. These results will facilitate studies of bacterial enzymes implicated in osmosensing and of other enzymes that are reconstituted in E. coli lipid vesicles.