Binding of sulfosuccinimidyl fatty acids to adipocyte membrane proteins: Isolation and ammo-terminal sequence of an 88-kD protein implicated in transport of long-chain fatty acids |
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Authors: | Caroll M Harmon Nada A Abumrad |
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Institution: | (1) Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 37232 Nashville, Tennessee;(2) Present address: Department of Physiology and Biophysics, State University of New York at Stony Brook, 11794-8661 Stony Brook, New York |
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Abstract: | Summary We recently reported (Harmon et al., J. Membrane Biol.
124:261–268, 1991) that sulfo-N-succinimidyl derivatives of long-chain fatty acids (SS-FA) specifically inhibited transport of oleate by rat adipocytes. These compounds bound to an 85–90 kD membrane protein which was also labeled by another inhibitor of FA transport 3H]DIDS (4,4-diisothiocyanostilbene-2-2-sulfonate). These results indicated that the protein was a strong candidate as the transporter for long-chain fatty acids. In this report we determined that the apparent size of the protein is 88 kD and its isoelectric point is 6.9. We used 3H]SS-oleate (SSO), which specifically labels the 88-kD protein, to isolate it from rat adipocyte plasma membranes. Identification of 15 amino acids at the N-terminus region revealed strong sequence homology with two previously described membrane glycoproteins: CD36, a ubiquitous protein originally identified in platelets and PAS IV, a protein that is enriched in the apical membranes of lipidsecreting mammary cells during lactation. Antibody against PAS IV cross-reacted with the adipocyte protein. This, together with the N-terminal sequence homology, suggested that the adipocyte protein belongs to a family of related intrinsic membrane proteins which include CD36 and PAS IV. |
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Keywords: | fatty acids transport adipocyte plasma membrane proteins Sulfosuccinimidyl fatty acid |
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