Nonlinear Electron Paramagnetic Resonance Studies of the Interaction of Cytochrome c Oxidase with Spin-Labeled Lipids in Gel-Phase Membranes

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• 作者：Tibor Pá ; li ; J&ouml ; rg H. Kleinschmidt ; Gary L. Powell ; and Derek Marsh
• 刊名：Biochemistry
• 出版年：2000
• 出版时间：March 7, 2000
• 年：2000
• 卷：39
• 期：9
• 页码：2355 - 2361
• 全文大小：83K
• 年卷期：v.39,no.9(March 7, 2000)
• ISSN：1520-4995

文摘

The interaction of lipids, spin-labeled at different positions in the sn-2 chain, with cytochromec oxidase reconstituted in gel-phase membranes of dimyristoylphosphatidylglycerol has been studied byelectron paramagnetic resonance (EPR) spectroscopy. Nonlinear EPR methods, both saturation transferEPR and progressive saturation EPR, were used. Interaction with the protein largely removes the flexibilitygradient of the lipid chains in gel-phase membranes. The rotational mobility of the chain segments isreduced, relative to that for gel-phase lipids, by the intramembranous interaction with cytochrome c oxidase.This holds for all positions of chain labeling, but the relative effect is greater for chain segments closerto the terminal methyl ends. Modification of the paramagnetic metal-ion centers in the protein by bindingazide has a pronounced effect on the spin-lattice relaxation of the lipid spin labels. This demonstratesthat the centers modified are sufficiently close to the first-shell lipids to give appreciable dipolar interactionsand that their vertical location in the membrane is closer to the 5-position than to the 14-position of thelipid chains.