jp072320b_si_001.mpg (4.38 MB)

Assembly of Lipids and Proteins into Lipoprotein Particles

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posted on 27.09.2007 by Amy Y. Shih, Anton Arkhipov, Peter L. Freddolino, Stephen G. Sligar, Klaus Schulten
The self-assembly of reconstituted discoidal high-density lipoproteins, known as nanodiscs, was studied using coarse-grained molecular dynamics and small-angle X-ray scattering. In humans, high-density lipoprotein particles transport cholesterol in the blood and facilitate the removal of excess cholesterol from the body. Native high-density lipoprotein exhibits a wide variety of shapes and sizes, forming lipid-free/poor, nascent discoidal, and mature spherical particles. Little is known about how these lipoprotein particles assemble and transform from one state to another. Multiple 10 μs coarse-grained simulations reveal the assembly of discoidal high-density lipoprotein particles from disordered protein−lipid complexes. Small-angle X-ray scattering patterns were calculated from the final assembled structures and compared with experimental measurements carried out for this study to verify the accuracy of the coarse-grained simulations. Results show that hydrophobic interactions assemble, within several microseconds, the amphipathic helical proteins and lipids into roughly discoidal particles, while the proteins assume a final approximate double-belt configuration on a slower time scale.