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Lipid Binding to the Amphipathic Membrane Protein Cytochrome b5

Peter J. Dehlinger, Patricia C. Jost and O. Hayes Griffith
Proceedings of the National Academy of Sciences of the United States of America
Vol. 71, No. 6 (Jun., 1974), pp. 2280-2284
Stable URL: http://www.jstor.org/stable/63406
Page Count: 5
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Lipid Binding to the Amphipathic Membrane Protein Cytochrome b5
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Abstract

The lipid binding properties of the membrane protein cytochrome b5 (detergent-extracted from calf liver microsomal preparations) were characterized by studying the interaction of spin-labeled lipids (5-, 12-, and 16-doxylstearic acid and 5- and 16-doxylphosphatidyl-choline, where doxyl refers to the nitroxide moiety) with cytochrome b5, using electron spin resonance spectroscopy. The intact cytochrome b5 molecule immobilizes all of the lipid spin labels, while the segment of cytochrome b5 released by trypsin does not affect lipid mobility. The immobilization of lipid spin labels on the hydrophobic surface of intact cytochrome b5 is not appreciably altered by associating the protein with liposomes. Differences in polarity of the lipid binding sites between cytochrome b5 and phospholipid vesicles were also observed. The lipid binding sites on cytochrome b5 are hydrophobic by conventional criteria, but are more polar than the interior of fluid phospholipid bilayers.

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