Apolipoprotein A-1's C-terminal domain contains a lipid sensitive conformational trigger Page: 3 of 22
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Structural Dynamics of Apolipoprotein A-I
The intrinsic conformational flexibility of exchangeable apolipoproteins allows their
existence in lipid-free and lipid-associated states. The C-terminal domain of human
apolipoproteinA-I (apoA-I), the major protein of high density lipoprotein (HDL), plays
an essential role in its lipid-binding and self-association. Site directed spin label electron
paramagnetic resonance spectroscopy was used to examine apoA-I's C-terminal
structure in both lipid-free and lipid-associated environments. By positioning a stable
free radical spin label at locations throughout the C-terminus, we identified the
presence of distinct secondary structural elements. Magnetic interactions of probes
localized at positions 163, 217, and 226 in single and double labeled apoA-I provided
inter/intra-molecular distance information, serving as the basis for mapping apoA-I
tertiary and quaternary structure. Spectra of labeled apoA-I in reconstituted HDL show
that lipid induces defined segments of random coil and -strand to transition to an
extended a-helix that presents a continuous hydrophobic surface. The conformational
transition of random coil to a-helix may serve as a means to overcome the energy
barriers of lipid sequestration, which has significant implications with respect to
cholesterol efflux, HDL assembly and cholesterol homeostasis.
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Oda, Michael N.; Forte, Trudy M.; Ryan, Robert O. & Voss, John C. Apolipoprotein A-1's C-terminal domain contains a lipid sensitive conformational trigger, article, December 17, 2002; Berkeley, California. (digital.library.unt.edu/ark:/67531/metadc779981/m1/3/: accessed November 24, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.