title: Phosphatidylethanolamine and phosphatidylglycerol are segregated into different domains in bacterial membrane. A study with pyrene-labelled phospholipids.
abstract: To detect and characterize membrane domains that have been proposed to exist in bacteria, two kinds of pyrene-labelled phospholipids, 2-pyrene-decanoyl-phosphatidylethanolamine (PY-PE) and 2-pyrene-decanoyl-phosphatidylglycerol (PY-PG) were inserted into Escherichia coli or Bacillus subtilis membrane. The excimerization rate coefficient, calculated from the excimer-to-monomer ratio dependencies on the probe concentration, was two times higher for PY-PE than for PY-PG at 37 degrees C. This was ascribed to different local concentrations rather than to differences in mobility. The extent of mixing between the two fluorescent phospholipids, estimated by formation of their heteroexcimer, was found very low both in E. coli and B. subtilis, in contrast to model membranes. In addition, these two pyrene derivatives exhibited different temperature phase transitions and different detergent extractability, indicating that the surroundings of these phospholipids in bacterial membrane differ in organization and order. Inhibition of protein synthesis, leading to condensation of nucleoid and presumably to dissipation of membrane domains, indeed resulted in increased formation of heteroexcimers, broadening of phase transitions and equal detergent extractability of both probes. It is proposed that in bacterial membranes these phospholipids are segregated into distinct domains that differ in composition, proteo-lipid interaction and degree of order; the proteo-lipid domain being enriched by PE.
authors.affiliation: Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Beer-Sheva 84105, Israel.
authors.forename: Sharon
authors.initials: S
authors.lastname: Vanounou
authors.forename: Abraham H
authors.initials: AH
authors.lastname: Parola
authors.forename: Itzhak
authors.initials: I
authors.lastname: Fishov
mesh_terms: D001412:Bacillus subtilis / Q000166:cytology / Q000378:metabolism; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism*; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism; D005456:Fluorescent Dyes / Q000378:metabolism*; D010714:Phosphatidylethanolamines / Q000378:metabolism*; D010715:Phosphatidylglycerols / Q000378:metabolism*; D014176:Protein Biosynthesis; D011721:Pyrenes / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: D005456:Fluorescent Dyes; D010714:Phosphatidylethanolamines; D010715:Phosphatidylglycerols; D011721:Pyrenes; C030984:pyrene