【原著】 ナノディスクのサイズ制御と安定性における アポA–Iへリックス構造の役割

抄録

Nanodiscs consist of phospholipids and scaffolding amphipathicα–helical proteins such as apolipoprotein A–I (apoA–I). To better understand the scaffolding function of apoA–I in nanodiscs, we examined the role of amino acid sequences in apoA–I to control the size and stability of nanodiscs using a series of deletion variants lacking different regions along the molecule. In cholate dialysis method, all apoA–I variants formed 1–palmitoyl–2–oleoyl phosphatidylcholine nanodiscs with diameters of 9～11 nm, in which the C–terminal deleted variant exhibited a poor ability to form nanodiscs. The nanodiscs of the C–terminal deleted variant were shown to be kinetically less stable compared to WT apoA–I nanodiscs, consistent with the importance of the C–terminal hydrophobic region in the formation of stable nanodiscs by apoA–I. Importantly, the correlation of the protein–to–phospholipid composition ratio with the number ofα–helical residues in the apoA–I variants on nanodiscs indicates that the lipid-holding capacity of apoA–I largely depends on the number ofα–helical residues on nanodiscs. These results imply the importance of theα– helix–forming ability of apoA–I in not only the energetics of the formation of nanodiscs but also the lipid–holding capacity of nanodiscs.