Size is a major determinant of dissociation and denaturation behaviour of reconstituted high-density lipoproteins

Abstract

Lipid-free apolipoprotein A-I (apoA-I) and A-I(Milano) (A-I(M)) were compared for their denaturation behaviour by running across transverse gradients of a chaotrope, urea, and of a ionic detergent, SDS. For both apo A-I and monomeric apoA-I(M) in the presence of increasing concentrations of urea the transition from high to low mobility had a sigmoidal course, whereas for dimeric A-I(M)/A-I(M) a non-sigmoidal shape was observed. The co-operativity of the unfolding process was lower for dimeric A-I(M)/A-I(M) than for apoA-I or for monomeric apoA-I(M). A slightly higher susceptibility to denaturation was observed for dimeric A-I(M)/A-I(M) than for monomeric apoA-I(M). A similar behaviour of A-I(M)/A-IM versus apoA-I(M) was observed in CD experiments. Large- (12.7/12.5 nm) and small- (7.8 nm) sized reconstituted high-density lipoproteins (rHDL) containing either apoA-I or A-I(M)/A-I(M) were compared with respect to their protein-lipid dissociation behaviour by subjecting them to electrophoresis in the presence of urea, of SDS and of a non-ionic detergent, Nonidet P40. A higher susceptibility to dissociation of small-sized versus large-sized rHDL, regardless of the apolipoprotein component, was observed in all three instances. Our data demonstrate that the differential plasticity of the various classes of rHDL is a function of their size; the higher stability of 12.5/12.7 nm rHDL is likely connected to the higher number of protein-lipid and lipid-lipid interactions in larger as compared with smaller rHDL.

Isolation, Characterization, and Stability of Discretely-Sized Nanolipoprotein Particles Assembled with Apolipophorin-III

“…A number of groups have investigated the spontaneous remodeling of apoA-I-based rHDLs over time [25] , [51] – [53] as well as resulting from actions by enzymes such as phospholipid transfer protein [54] , lecithin:cholesterol acyltransferase [55] , and cholesteryl ester transfer protein [56] . Although anticipated based on the observations made with apoA-I, no evidence of the remodeling of apoLp-III based particles has been reported.…”

Effects of Mutations in Apolipoprotein C-1 on the Reconstitution and Kinetic Stability of Discoidal Lipoproteins

“…Structural stability is essential for HDL functions in lipid transport and metabolism and in the pathogenesis of atherosclerosis and hypertriglyceridemia (9), yet molecular mechanisms of lipoprotein stabilization are not clearly understood. Most existing reports on lipoprotein stability are based upon the equilibrium thermodynamic approach (for recent reviews see refs [9][10][11][12][13][14][15]. However, our recent analyses of model discoidal HDL (16) and spherical human plasma HDL (17), supported by several earlier studies (18)(19)(20), have shown that, contrary to the widely held assumption, HDL stability has a kinetic rather than a thermodynamic origin.…”

Apolipoprotein A‐IMilano anion exchange chromatography: Self association and adsorption equilibrium

“…Although a reasonable fit is achieved, this model under-predicts association at low protein concentrations and overpredicts it at higher concentrations. The second model is empirical and assumes that tetramer formation is represented by: (4) while keeping the same expression as before for the formation of hexamer. Accordingly, we have:…”

“…Apolipoprotein A-I is a physiologically important, lipid-binding protein that is the major protein constituent of high density lipoprotein (HDL) involved in cholesterol transport [1][2][3]. It is comprised of a single chain of 243 amino acids with 8 repeating sequences of 22 amino acids forming amphipathic αhelices and 2 tandem repeats of 11 amino acids that enable the protein to bind lipids [3].Apolipoprotein A-I Milano (apoA-I M ) is a naturally occurring variant of apolipoprotein A-I with a cysteine substituted for arginine at position 173 [3][4][5]. When oxidized, apoA-I M consists of a homodimer, with a disulfide bridge connecting two monomers, which reversibly self-associates to higher order species.…”