Novel spin-labels for the study of lipid-protein interactions. Application to (Na+, K+)-ATPase membranes.
The interactions of a series of spin-labeled fatty acids, in which the nitroxide ring is incorporated in different ways as an integral part of the hydrocarbon chain, with the (Na+,K+)-ATPase in membranes from Squalus acanthias, have been studied by electron spin resonance spectroscopy. The fatty acids are 2,4-, 2,5-, and 3,2-substituents of 2,2,5,5-tetramethylpyrrolidine-N-oxyl and belong to the class of minimal perturbation nitroxide probes. For all five fatty acid labels, a motionally restricted lipid component was observed in the ESR spectra of (Na+,K+)-ATPase membranes, in addition to the fluid component, which was found in the spectra of the extracted membrane lipids. The pH dependence of the motionally restricted spin-label population indicated a sensitivity in the selectivity of the lipid-protein interaction to the protonation state of the fatty acid. These results agree with those found previously for the conventional oxazolidine (doxyl) fatty acid and phospholipid spin-label derivatives [Esmann, M., Watts, A., & Marsh, D. (1985) Biochemistry 24, 1386-1393] and indicate that the motion of the lipid chains is significantly hindered by interaction with the protein, irrespective of the nature of the spin-label group.
Esmann
M
M
Abteilung Spektroskopie, Max-Planck-Institut für biophysikalische Chemie, Göttingen, Federal Republic of Germany.
Hideg
K
K
Marsh
D
D
D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D004284:Dogfish; D004578:Electron Spin Resonance Spectroscopy; D008563:Membrane Lipids / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013113:Spin Labels; D013696:Temperature
D008563:Membrane Lipids; D008565:Membrane Proteins; D013113:Spin Labels; D000254:Sodium-Potassium-Exchanging ATPase