A detailed molecular belt model for apolipoprotein A-I in discoidal high density lipoprotein
Faculty of Pharmaceutical, Biomedical and Veterinary Sciences. Pharmacy
Journal of biological chemistry. - Baltimore, Md
, p. 31755-31758
Apolipoprotein A-I (apoA-I) is the principal protein of high density lipoprotein particles (HDL). ApoA-I contains a globular N-terminal domain (residues 143) and a lipid-binding C-terminal domain (residues 44243). Here we propose a detailed model for the smallest discoidal HDL, consisting of two apoA-I molecules wrapped beltwise around a small patch of bilayer containing 160 lipid molecules. The C-terminal domain of each monomer is ringlike, a curved, planar amphipathic α helix with an average of 3.67 residues per turn, and with the hydrophobic surface curved toward the lipids. We have explored all possible geometries for forming the dimer of stacked rings, subject to the hypothesis that the optimal geometry will maximize intermolecular salt bridge interactions. The resulting model is an antiparallel arrangement with an alignment matching that of the (nonplanar) crystal structure of lipid-free apoA-I.