Constitutive expression of a saturable transport system for non-esterified fatty acids in Xenopus laevis oocytes.
In the presence of 150 microM BSA, uptake of [3H]oleate by Xenopus laevis oocytes was a saturable function of the unbound oleate concentration (Vmax. 110 +/- 4 pmol/h per oocyte; Km 193 +/- 11 nM unbound oleate). Oleate uptake was three orders of magnitude faster than that of another test substance, [35S]bromosulphophthalein, and was competitively inhibited by 55 nM unbound palmitate (Vmax. 111 +/- 14 pmol/h per oocyte; Km 424 +/- 63 nM unbound oleate) (P < 0.01). Oleate uptake was also inhibited by antibodies to a 43 kDa rat liver plasma-membrane fatty acid-binding protein, a putative transporter of long-chain fatty acids in mammalian cells; uptake of the medium-chain fatty acid [14C]octanoate was unaffected. Immunofluorescence and immunoblotting demonstrated that the antiserum reacted with a single 43 kDa protein on the oocyte surface. Hence a protein related to the mammalian plasma-membrane fatty acid-binding protein may play a role in saturable uptake of long-chain fatty acids by Xenopus oocytes.
Zhou
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Department of Medicine Division of Liver Disease, Mount Sinai School of Medicine, New York, NY 10029.
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D000818:Animals; D001692:Biological Transport; D015153:Blotting, Western; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000378:metabolism; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005455:Fluorescent Antibody Technique; D008565:Membrane Proteins / Q000378:metabolism; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D019301:Oleic Acid; D009829:Oleic Acids / Q000378:metabolism; D009865:Oocytes / Q000378:metabolism*; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D014982:Xenopus laevis
D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005230:Fatty Acids, Nonesterified; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D009829:Oleic Acids; D010169:Palmitic Acids; D019301:Oleic Acid; D019308:Palmitic Acid