Sterol domains in phospholipid membranes: dehydroergosterol polarization measures molecular sterol transfer.
The domain structure of cholesterol in membranes and factors affecting it are not well understood. A method, based on kinetics of delta 5,7,9,(11),22-erogostatetraen-3 beta-ol (dehydroergosterol) fluorescence polarization change and not requiring separation of donor and acceptor membranes, was used to examine sterol domains in three-component cholesterol:dehydroergosterol:phospholipid small unilamellar vesicles (SUV). A new mathematical data treatment was developed to provide a direct correlation between molecular sterol exchange and steady-state dehydroergosterol fluorescence polarization measurements. The method identified multiple kinetic pools of sterol in SUV: a small but rapidly exchanging pool, a predominant slowly exchanging pool, and a very slowly exchangeable (nonexchangeable) pool. The relative sizes of the pools and half-times of exchange were highly dependent on the presence of acidic phospholipids and on cytosolic proteins involved in sterol transfer. Thus, the method provides a direct measure of molecular sterol transfer between membranes without separating donor and acceptor membranes.
Butko
P
P
Dept. Pharm. and Cell Biophysics, University of Cincinnati Medical Center, Ohio 45267-0004.
Hapala
I
I
Nemecz
G
G
Schroeder
F
F
D001692:Biological Transport; D002352:Carrier Proteins / Q000737:chemistry; D004875:Ergosterol / Q000031:analogs & derivatives* / Q000737:chemistry; D005454:Fluorescence Polarization; D007700:Kinetics; D008051:Lipid Bilayers / Q000737:chemistry; D008560:Membrane Fluidity; D008563:Membrane Lipids / Q000737:chemistry*; D010713:Phosphatidylcholines / Q000737:chemistry; D010743:Phospholipids / Q000737:chemistry*; D010940:Plant Proteins
D002352:Carrier Proteins; D008051:Lipid Bilayers; D008563:Membrane Lipids; D010713:Phosphatidylcholines; D010743:Phospholipids; D010940:Plant Proteins; C072087:sterol carrier proteins; C010905:dehydroergosterol; C028694:1-palmitoyl-2-oleoylphosphatidylcholine; D004875:Ergosterol