title: High-density lipoprotein binding to bovine adrenal cortex membranes.
abstract: Binding studies were performed with bovine adrenal cortex membranes, human 125I-labelled high-density lipoprotein (HDL) and modified photoactivable derivatives of 125I-labelled HDL, namely 125I-labelled HDL-amidinophenylazide and 125I-labelled HDL-amidopropionyldithiophenylazide. The purity of the apolipoprotein composition of the 125I-labelled HDL and photoactivable 125I-labelled HDL used in the binding studies was determined by Coomassie blue and silver staining, and by measuring 125I-labelled cpm after SDS-polyacrylamide gel electrophoresis. About 45% of the 125I-labelled HDL binding to the membranes occurred in the presence of excess EDTA and only unlabelled HDL competed for the binding site. The 125I-labelled interaction with this binding site on the membranes did not require calcium. In addition, 40% of the 125I-labelled HDL binding was to an EDTA-sensitive site, and unlabelled HDL and low-density lipoprotein (LDL) competed for the binding site. Consequently, adrenal cortex membranes have binding sites which show cross reactivity for both HDL and LDL. Modification of 58% of the apolipoprotein lysine residues of 125I-labelled HDL with methylazidophenylimidate, a reagent which maintains the positive charge at lysine residues, had little affect on binding to EDTA-sensitive and insensitive sites. In contrast, modification of 35% of apolipoprotein lysine residues of 125I-labelled HDL with N-succinimidyl(4-azidophenyldithio)propionate, a reagent which converts charged amino lysines to amide bonds, showed binding properties which were almost totally inhibited by EDTA.
mesh_terms: D000302:Adrenal Cortex / Q000378:metabolism*; D000818:Animals; D001386:Azides / Q000378:metabolism; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002352:Carrier Proteins; D002417:Cattle; D003432:Cross-Linking Reagents / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D007096:Imidoesters / Q000378:metabolism; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008077:Lipoproteins, LDL / Q000378:metabolism; D008239:Lysine / Q000378:metabolism; D008566:Membranes / Q000378:metabolism; D010782:Photolysis; D016601:RNA-Binding Proteins; D011956:Receptors, Cell Surface / Q000378:metabolism; D018110:Receptors, Lipoprotein
chemical_list: D001386:Azides; D002352:Carrier Proteins; D003432:Cross-Linking Reagents; D007096:Imidoesters; D008075:Lipoproteins, HDL; D008077:Lipoproteins, LDL; D016601:RNA-Binding Proteins; D011956:Receptors, Cell Surface; D018110:Receptors, Lipoprotein; C031616:high density lipoprotein receptors; C075197:high density lipoprotein binding protein; C026810:methyl 4-azidobenzimidate; C033169:3-((4-azidophenyl)dithio)propionic N-hydroxysuccinimide; D004492:Edetic Acid; D008239:Lysine; D002118:Calcium