Apolipoprotein A‐I‐binding protein from human term placenta Purification and partial characterization

Abstract

A protein that binds to the main apoprotein, apoA‐I, of human high density lipoprotein (HDL) has been isolated from human placenta. Ligand blotting after SDS gel electrophoresis indicated that the 120 kDa protein in the absence of reducing agents binds apoA‐I. If gel electrophoresis was performed under reducing conditions two main bands, approx. 50 and 30 kDa that did not bind apoA‐I, were evident. In an enzyme‐linked immunosorbent assay the binding protein specifically bound apoA‐I, delipidated or as HDL. ApoA‐II, apo E and LDL did not compete with apoA‐I for binding to this protein.

Studies on the proteins involved in the interaction of high‐density lipoprotein with isolated human small intestine epithelial cells

“…Several attempts have been undertaken to identify determinants in both HDL [5] and its putative receptor [7][8][9][10]. These studies have, however, not resulted in a consensus for the identities of specific determinants involved in this interaction.…”

“…In the present work we have tried to address this question using antibodies against two potential ligands, ape A-I and ape A-II. and also against a potential receptor, an ape A-I-BP from human placenta [9].…”

“…The preparation and characterization of polyclonal anti-ape A.I and anti.ape A-II antibodies [13], and antibody against ape A-1-BP [9] has been described previously.…”

“…Proteins which specifically bind ape A-I and HDL have been isolated and partially characterized from a number of cells, These proteins may represent the putative HDL receptor or parts thereof [7][8][9][10]. One of these proteins, isolated from human placenta by affinity chromatography, specifically bound to ape A-I and was designated as ape A-I-binding protein (ape A-I-BP) [9].…”

“…One of these proteins, isolated from human placenta by affinity chromatography, specifically bound to ape A-I and was designated as ape A-I-binding protein (ape A-I-BP) [9].…”