title: Volumetric determination of apolipoprotein stoichiometry of circulating HDL subspecies.
abstract: Although HDL is inversely correlated with coronary heart disease, elevated HDL-cholesterol is not always protective. Additionally, HDL has biological functions that transcend any antiatherogenic role: shotgun proteomics show that HDL particles contain 84 proteins (latest count), many correlating with antioxidant and anti-inflammatory properties of HDL. ApoA-I has been suggested to serve as a platform for the assembly of these protein components on HDL with specific functions - the HDL proteome. However, the stoichiometry of apoA-I in HDL subspecies is poorly understood. Here we use a combination of immunoaffinity chromatography data and volumetric analysis to evaluate the size and stoichiometry of LpA-I and LpA-I,A-II particles. We conclude that there are three major LpA-I subspecies: two major particles, HDL[4] in the HDL3 size range (d = 85.0 ± 1.2 Å) and HDL[7] in the HDL2 size range (d = 108.5 ± 3.8 Å) with apoA-I stoichiometries of 3 and 4, respectively, and a small minor particle, HDL[1] (d = 73.8 ± 2.1Å) with an apoA-I stoichiometry of 2. Additionally, we conclude that the molar ratio of apolipoprotein to surface lipid is significantly higher in circulating HDL subspecies than in reconstituted spherical HDL particles, presumably reflecting a lack of phospholipid transfer protein in reconstitution protocols.
authors.affiliation: Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294; and.
authors.forename: Jere P
authors.initials: JP
authors.lastname: Segrest
authors.forename: Marian C
authors.initials: MC
authors.lastname: Cheung
authors.forename: Martin K
authors.initials: MK
authors.lastname: Jones
mesh_terms: D016632:Apolipoprotein A-I / Q000097:blood*; D016633:Apolipoprotein A-II / Q000097:blood*; D002846:Chromatography, Affinity; D005260:Female; D006801:Humans; D017270:Lipoprotein(a) / Q000097:blood; D008075:Lipoproteins, HDL / Q000097:blood* / Q000737:chemistry / Q000302:isolation & purification; D008297:Male; D063347:Native Polyacrylamide Gel Electrophoresis; D010316:Particle Size; D013499:Surface Properties; D014461:Ultracentrifugation
chemical_list: D016632:Apolipoprotein A-I; D016633:Apolipoprotein A-II; D017270:Lipoprotein(a); D008075:Lipoproteins, HDL
keywords: HDL platform; HDL surface monolayer; LpA-I; LpA-I,A-II; apolipoprotein A-I; apolipoprotein A-II; reconstituted spheroidal HDL