Solution structure of discoidal high-density lipoprotein particles with a shortened apolipoprotein A-I

Area of Science:

• Biochemistry
• Structural Biology
• Lipid Metabolism

Background:

• High-density lipoprotein (HDL) particles are crucial for reverse cholesterol transport.
• Discoidal HDL particles are key intermediates in HDL maturation and cholesterol uptake.
• Understanding HDL structure is vital for metabolic disease research.

Purpose of the Study:

• To determine the three-dimensional structure of reconstituted discoidal HDL (rdHDL) particles.
• To elucidate the structural role of apolipoprotein A-I in HDL assembly and lipid binding.
• To provide insights into the mechanism of cholesterol transport by HDL.

Main Methods:

• Reconstitution of discoidal HDL particles using a shortened human apolipoprotein A-I construct.
• Determination of the 3D structure using nuclear magnetic resonance (NMR), electron paramagnetic resonance (EPR), and transmission electron microscopy (TEM).

Main Results:

• The rdHDL particles exhibit a protein double belt structure formed by apolipoprotein A-I.
• This protein belt surrounds a lipid bilayer patch in an antiparallel arrangement.
• Structural integrity is maintained by salt bridges and cation-π interactions, with helix rotation accommodating lipid loading.

Conclusions:

• The determined structure explains the functional complexity of HDL as a lipid shuttle.
• The findings highlight the intricate protein-lipid interactions essential for cholesterol transport.
• This structural insight aids in understanding HDL's role in lipid homeostasis and atherosclerosis.