title: The binding of haptoglobin to apolipoprotein AI: influence of hemoglobin and concanavalin A.
abstract: Haptoglobin (Hp) can be purified by affinity chromatography using hemoglobin (Hb)-linked Sepharose. Elution with 8 M urea is generally performed, resulting in heavy contamination of the Hp preparation by apolipoprotein AI (ApoAI), and partial loss of Hb binding activity. Hp, separated from ApoAI, was recovered by elution with glycine-HCl at pH 3. Complexes of the isolated protein with Hb or ApoAI were detected by enzyme-linked immunosorbent assay (ELISA). Competition between the two ligands in their interaction with Hp was observed. Concanavalin A (ConA), which binds the Hp carbohydrate chains, did not influence Hp binding to ApoAI. These results suggest that changes in the plasma levels of ApoAI or Hb affect the Hp role in regulating the reverse transport of cholesterol or preventing Hb-dependent oxidative damage.
authors.affiliation: Dipartimento di Fisiologia Generale ed Ambientale, Università di Napoli Federico II, I-80134 Napoli, Italy.
authors.forename: Maria Stefania
authors.initials: MS
authors.lastname: Spagnuolo
authors.forename: Luisa
authors.initials: L
authors.lastname: Cigliano
authors.forename: Paolo
authors.initials: P
authors.lastname: Abrescia
mesh_terms: D016632:Apolipoprotein A-I / Q000737:chemistry / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D002846:Chromatography, Affinity; D003208:Concanavalin A / Q000737:chemistry / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006242:Haptoglobins / Q000737:chemistry / Q000378:metabolism*; D006454:Hemoglobins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D010949:Plasma / Q000737:chemistry; D011485:Protein Binding
chemical_list: D016632:Apolipoprotein A-I; D006242:Haptoglobins; D006454:Hemoglobins; D003208:Concanavalin A