title: Spin-label studies of lipid-protein interactions in (Na+,K+)-ATPase membranes from rectal glands of Squalus acanthias.
abstract: Lipid-protein interactions in (Na+,K+)-ATPase-rich membranes from the rectal gland of Squalus acanthias have been studied by using spin-labeled lipids in conjunction with electron spin resonance (ESR) spectroscopy. Lipid-protein associations are revealed by the presence of a second component in the ESR spectra of the membranes in addition to a component which corresponds very closely to the ESR spectra obtained from dispersions of the extracted membrane lipids. This second component corresponds to spin-labeled lipids whose motion is very significantly restricted relative to that of the fluid lipids in the membrane or the lipid extract. A stoichiometry of approximately 66 lipids per 265 000-dalton protein is found for the motionally restricted component of those spin-labeled lipids (e.g., phosphatidylcholine) which show least specificity for the protein. This corresponds approximately to the number of lipids which may be accommodated within the first shell around the alpha 2 beta 2 protein dimer. A selectivity of the various spin-labeled lipids for the motionally restricted component associated with the protein is found in the following order: cardiolipin greater than phosphatidylserine approximately stearic acid greater than or equal to phosphatidic acid greater than phosphatidylglycerol approximately phosphatidylcholine approximately phosphatidylethanolamine approximately androstanol.
authors.forename: M
authors.initials: M
authors.lastname: Esmann
authors.forename: A
authors.initials: A
authors.lastname: Watts
authors.forename: D
authors.initials: D
authors.lastname: Marsh
mesh_terms: D000818:Animals; D003080:Cold Temperature; D004284:Dogfish; D004578:Electron Spin Resonance Spectroscopy; D008433:Mathematics; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D012007:Rectum; D012491:Salt Gland / Q000201:enzymology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D008563:Membrane Lipids; D008565:Membrane Proteins; D000254:Sodium-Potassium-Exchanging ATPase