title: Regulation of carnitine binding to plasma membranes by an ATP-dependent mechanism.
abstract: This is the first demonstration of L-carnitine binding to plasma membranes. Plasma membranes derived from S49 lymphoma cells bound 40.6 +/- 5.7 pmol carnitine/ mg membrane protein under basal conditions whereas addition of ATP in the presence of magnesium ions increased the number of carnitine binding sites to 557 +/- 82 pmol/mg membrane protein, i.e., a 10-fold increase. Kinetic and equilibrium binding data indicated heterogeneity of carnitine binding sites. ATP modulated carnitine binding sites through a single class of sites at a KD of 20.7 +/- 3.5 microM. The ATP effect seemed mediated by a protein tyrosine kinase as judged from the observed noncompetive inhibition of carnitine binding induced by genistein with a Ki = 65 +/- 11 microM. Active cellular uptake of L-carnitine in S49 lymphoma cells was similarly reduced from 580 +/- 35 to 421 +/- 39 pmol/mg protein/h by genistein.
authors.affiliation: Wallenberg Laboratory, Gothenburg University, Sahlgren's Hospital, Göteborg, Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Gustafson
authors.forename: L A
authors.initials: LA
authors.lastname: Ransnäs
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D001665:Binding Sites; D002331:Carnitine / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D019833:Genistein; D007529:Isoflavones / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors; D011869:Radioligand Assay; D013347:Subcellular Fractions / Q000378:metabolism; D014316:Tritium; D014407:Tumor Cells, Cultured
chemical_list: D004791:Enzyme Inhibitors; D007529:Isoflavones; D014316:Tritium; D000255:Adenosine Triphosphate; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D002331:Carnitine