CONFIGURATION OF APOLIPOPROTEIN A-I IN DISCOIDAL HIGH DENSITY LIPOPROTEIN SPONTANEOUSLY GENERATED BY THE REACTION WITH DMPC VESICLES

CUELLAR, LUZ ANGELA; PRIETO, EDUARDO DANIEL; GARDA, HORACIO ALBERTO

Búzios- Rio de Janeiro- Brasil (3-9-2009/3-10-2009)

Congreso; VII Iberoamarican Congress of Biophysics 2009; 2009

Discoidal high density lipoproteins (dHDL) are very important intermediates in cell lipid efflux mediated by apolipoprotein A-I (apoAI). Due to the difficulty in isolating cell-generated dHDL, all the structural knowledge about these particles comes from studies in artificially reconstituted dHDL. The most used method for dHDL reconstitution is detergent dialysis, but dHDL are also spontaneously generated by the reaction with phospholipid vesicles within the temperature range of the gel/liquid-crystalline phase transition (Tt), a process that may have similarities to that occurring in vivo. Several experimental evidence in reconstituted dHDL supports the ?double belt? model, in which each one of two ring-shaped apoAI molecules wrap around a lipid bilayer disc in an anti-parallel orientation for dHDL obtained by cholate-dialysis. Different studies support the belt model with a variable helix register. Lysine cross-linking combined with MS detects the presence of at least two coexisting arrangements differing in the alignment between both apoAI monomers (see Fig 1). In the predominant form (5/5 configuration), helices 5 of each apoAI monomer are close together each other. In a minor detected form (5/2 configuration), helix 5 in one monomer is close together with helix 2 in the other one.