title: C-terminus of apolipoprotein A-I removes phospholipids from a triolein/phospholipids/water interface, but the N-terminus does not: a possible mechanism for nascent HDL assembly.
abstract: Apolipoprotein A-I (ApoA-I) is the principle protein component of HDL, also known as "good cholesterol," which is an inverse marker for cardiovascular disease. The N-terminal 44 amino acids of ApoA-I (N44) are predicted to be responsible for stabilization of soluble ApoA-I, whereas the C-terminal 46 amino acids (C46) are predicted to initiate lipid binding and oligomerization. In this work, we apply what we believe to be a novel application of drop tensiometry to study the adsorption and desorption of N44 and C46 at a triolein/POPC/water (TO/POPC/W) interface. The amount of peptide that adsorbed to the surface was dependent on the surface concentration of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) and pressure (Π) before adsorption. At a TO/POPC/W interface, the exclusion pressure (Π(EX)) of C46 was 25.8 mN/m, and was 19.3 mN/m for N44. Once adsorbed, both peptides formed a homogeneous surface with POPC but were progressively ejected from the surface by compression. During a compression, C46 removed POPC from the surface whereas N44 did not. Repeated compressions caused C46 to deplete entirely the surface of phospholipid. If full-length ApoA-I could also remove phospholipid, this could provide a mechanism for the transfer of surface components of chylomicrons and very low density lipoprotein to high density lipoprotein with the assistance of phospholipid transfer protein.
authors.affiliation: Department of Physiology and Biophysics, Boston University School of Medicine, Boston, Massachusetts, USA.
authors.forename: Matthew A
authors.initials: MA
authors.lastname: Mitsche
authors.forename: Donald M
authors.initials: DM
authors.lastname: Small
mesh_terms: D000327:Adsorption; D016632:Apolipoprotein A-I / Q000737:chemistry* / Q000378:metabolism*; D053442:High-Density Lipoproteins, Pre-beta / Q000378:metabolism*; D008958:Models, Molecular; D010455:Peptides / Q000378:metabolism; D010713:Phosphatidylcholines / Q000737:chemistry*; D010743:Phospholipids / Q000302:isolation & purification*; D013329:Structure-Activity Relationship; D013696:Temperature; D014304:Triolein / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D016632:Apolipoprotein A-I; D053442:High-Density Lipoproteins, Pre-beta; D010455:Peptides; D010713:Phosphatidylcholines; D010743:Phospholipids; D014867:Water; D014304:Triolein; C028694:1-palmitoyl-2-oleoylphosphatidylcholine