Isolation of myocardial membrane long-chain fatty acid-binding protein: homology with a rat membrane protein implicated in the binding or transport of long-chain fatty acids.
Abnormal myocardial long-chain fatty acid uptake is suspected of being involved in certain types of heart disease, but the mechanism by which the heart takes up long-chain fatty acids remains unclear. The sulfo-N-succinimidyl derivatives of long-chain fatty acids have been reported to undergo covalent binding to a membrane protein and to irreversibly inhibit the transport of long-chain fatty acids by rat adipocytes (Harmon et al., 1991). It has been suggested that the membrane protein bound by these derivatives is a candidate transporter for long-chain fatty acids in adipocytes. However, myocardial membrane long-chain fatty acid-binding proteins have not yet been fully investigated. Rat hearts were isolated and perfused with a sulfo-N-succinimidyl derivative of tritium-labeled palmitate ([3H]SSP). Then the [3H]SSP-binding protein was characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) autoradiography and histological autoradiography. Myocardial palmitic acid uptake was examined after pretreatment of isolated perfused rat hearts with SSP. The SSP-binding protein was isolated from bovine hearts by successive chromatography, and the amino acid sequences of lysylendopeptidase-digested peptide fragments were determined. SDS-PAGE autoradiography revealed that [3H]SSP bound to an 85-90 kDa protein derived from the myocardial microsomal fraction, and histological autoradiography demonstrated that [3H]SSP radioactivity was localized to the myocardial cell membrane. Pre-incubation with SSP inhibited palmitic acid uptake by isolated perfused rat hearts. A [3H]SSP-binding protein was also found in canine and bovine hearts, and was isolated from the bovine cardiac membrane fraction. Amino acid sequencing revealed that four peptide fragments showed strong sequence homology with rat adipocyte membrane protein, which is implicated in the binding or transport of long-chain fatty acids (Abumrad et al., 1993). We conclude that the SSP-binding protein is localized to the myocardial cell membrane and might be involved in the uptake or transport of long-chain fatty acids.
Department of Internal Medicine, Osaka Medical College, Japan.
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Tanaka
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Kawamura
D000595:Amino Acid Sequence; D000818:Animals; D001345:Autoradiography / Q000379:methods; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D002417:Cattle; D002462:Cell Membrane / Q000378:metabolism; D002852:Chromatography, Ion Exchange; D004285:Dogs; D004591:Electrophoresis, Polyacrylamide Gel; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005230:Fatty Acids, Nonesterified / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D008861:Microsomes / Q000378:metabolism; D008969:Molecular Sequence Data; D018996:Myelin P2 Protein / Q000187:drug effects / Q000302:isolation & purification / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010168:Palmitates / Q000378:metabolism* / Q000494:pharmacology; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000302:isolation & purification; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D013388:Succinimides / Q000378:metabolism* / Q000494:pharmacology
D002352:Carrier Proteins; C490174:Fabp7 protein, rat; D000071438:Fatty Acid-Binding Protein 7; D050556:Fatty Acid-Binding Proteins; D005230:Fatty Acids, Nonesterified; D018996:Myelin P2 Protein; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D010168:Palmitates; D010169:Palmitic Acids; D010446:Peptide Fragments; D013388:Succinimides; C097197:sulfo-N-succinimidyl palmitate; D019308:Palmitic Acid; D005947:Glucose