APOEは299アミノ酸からなり、複数の両親媒性αヘリックスを持つ。結晶構造解析によると、蝶番領域がN末端とC末端領域を接続している。N末端領域(1-167アミノ酸)は、非極性の側面がタンパク質の内側を向いた逆並行の4ヘリックスバンドルを形成する。一方、C末端ドメイン(206-299アミノ酸)は、3つのαヘリックスを持ち、これが大きな疎水性表面を形成してN末端のヘリックスバンドルと水素結合や塩橋を介して相互作用する。C末端領域は、低密度リポタンパク質受容体(low density lipoprotein receptor、LDLR)結合サイトも持つ[13]。
遺伝子多型
APOE遺伝子には主に3つの対立遺伝子(ε2、ε3、ε4[14][15])がある。3種類の対立遺伝子産物は112番目と158番目のアミノ酸が1つまたは2つ違うだけだが[16][17][18](APOE-ε2 (cys112, cys158), APOE-ε3 (cys112, arg158), and APOE-ε4 (arg112, arg158)[10][19][20])、この違いによりAPOEの構造や機能も変化する。
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