The low-resolution structure of nHDL reconstituted with DMPC with and without cholesterol reveals a mechanism for particle expansion

• DOI: 10.1194/jlr.m032763
• Publication Date: 2013-01-25T01:17:44Z
• Authors: Valentin Gogonea; Gary S. Gerstenecker; Zhiping Wu; Xavier Lee; Celalettin Topbas; Matthew A. Wagner; Thomas C. Tallant; Jonathan D. Smith; Philip Callow; Vitaliy Pipich; Hélène Malet; Guy Schoehn; Joseph A. DiDonato; Stanley L. Hazen
• Keywords: Small Angle; 0301 basic medicine; MESH: Apolipoprotein A-I; QD415-436; High-Density Lipoproteins, Pre-beta; Biochemistry; [SDV.BBM.BS]Life Sciences [q-bio]/Biochemistry; Mass Spectrometry; MESH: Dimyristoylphosphatidylcholine; 03 medical and health sciences; MESH: Cholesterol; Pre-beta; apolipoprotein A1; Scattering, Small Angle; Humans; MESH: Scattering, Small Angle; MESH: Mass Spectrometry; MESH: Humans; small-angle neutron scattering; [SDV.BBM.BS]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Structural Biology [q-bio.BM]; Apolipoprotein A-I; Molecular Biology/Structural Biology [q-bio.BM]; dimyristoyl phosphatidylcholine; nascent high density lipoprotein; 540; MESH: High-Density Lipoproteins, Pre-beta; Cholesterol; MESH: Scattering; MESH: High-Density Lipoproteins; Dimyristoylphosphatidylcholine

Small-angle neutron scattering (SANS) with contrast variation was used to obtain the low-resolution structure of nascent HDL (nHDL) reconstituted dimyristoyl phosphatidylcholine (DMPC) in absence and presence cholesterol, [apoA1:DMPC (1:80, mol:mol) apoA1:DMPC:cholesterol (1:86:9, mol:mol:mol)]. The overall shape both particles is discoidal apoA1 visualized as an open, contorted, out plane conformation three arms HDL/dimyristoyl without cholesterol (nHDLDMPC) two (nHDLDMPC+Chol). lipid phase nHDLDMPC nHDLDMPC+Chol were oblate ellipsoids, fit well within their respective protein shapes. Modeling studies indicate that folded onto itself nHDLDMPC, making a large hairpin, which also confirmed independently by cross-linking mass spectrometry hydrogen-deuterium exchange (HDX) analyses. In nHDLDMPC+Chol, expanded no hairpin visible. Importantly, despite whole particle open (i.e., not closed belt) observed. 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