Fluorescence energy transfer study of the lipid bilayer interactions with truncated apolipoprotein a-i mutants
Keywords:
Förster resonance energy transfer, lipid bilayer, Thioflavin T, apolipoprotein A-I.Abstract
Förster resonance energy transfer (FRET) between anthrylvinyl-labeled phosphatidylcholine (AV-PC) as
a donor and Thioflavin T (ThT) as an acceptor has been employed to explore the binding of N-terminal
fragments of wild (A83) and amyloidogenic variants of apolipoprotein A-I (apoA-I) with substitution
mutations G26R, G26R/W@8, G26R/W@50 and G26R/W@72 to the model membranes composed of
phosphatidylcholine (PC). Analysis of the experimental data in terms of 2D FRET model combined with
the partition model revealed that ThT distance from the lipid bilayer center falls in the range 1.7-2.5 nm,
suggesting that the dye is located in the interfacial membrane region, at the level of phospholipid
headgroups, while partition coefficient characterizing ThT distribution between the aqueous and lipid
phases was estimated to be ca. 4×102. Interaction of monomeric apoA-I N-terminal fragments with PC
liposomes resulted in the increase of AV-ThT FRET efficiency, while this parameter displayed
ambiguous behavior upon membrane binding of fibrillar apoA-I mutants. These findings were
rationalized in terms of the existence of discrete lipid-binding sites within the fibril structure. It was
demonstrated that FRET technique can be employed for ascertaining specific modes of fibril-membrane
interactions.
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