ジャーナル: Nature / 年: 2020 タイトル: Structure of nevanimibe-bound tetrameric human ACAT1. 著者: Tao Long / Yingyuan Sun / Abdirahman Hassan / Xiaofeng Qi / Xiaochun Li / 要旨: Cholesterol is an essential component of mammalian cell membranes, constituting up to 50% of plasma membrane lipids. By contrast, it accounts for only 5% of lipids in the endoplasmic reticulum (ER). ...Cholesterol is an essential component of mammalian cell membranes, constituting up to 50% of plasma membrane lipids. By contrast, it accounts for only 5% of lipids in the endoplasmic reticulum (ER). The ER enzyme sterol O-acyltransferase 1 (also named acyl-coenzyme A:cholesterol acyltransferase, ACAT1) transfers a long-chain fatty acid to cholesterol to form cholesteryl esters that coalesce into cytosolic lipid droplets. Under conditions of cholesterol overload, ACAT1 maintains the low cholesterol concentration of the ER and thereby has an essential role in cholesterol homeostasis. ACAT1 has also been implicated in Alzheimer's disease, atherosclerosis and cancers. Here we report a cryo-electron microscopy structure of human ACAT1 in complex with nevanimibe, an inhibitor that is in clinical trials for the treatment of congenital adrenal hyperplasia. The ACAT1 holoenzyme is a tetramer that consists of two homodimers. Each monomer contains nine transmembrane helices (TMs), six of which (TM4-TM9) form a cavity that accommodates nevanimibe and an endogenous acyl-coenzyme A. This cavity also contains a histidine that has previously been identified as essential for catalytic activity. Our structural data and biochemical analyses provide a physical model to explain the process of cholesterol esterification, as well as details of the interaction between nevanimibe and ACAT1, which may help to accelerate the development of ACAT1 inhibitors to treat related diseases.
電子線照射量: 60 e/Å2 / フィルム・検出器のモデル: GATAN K3 (6k x 4k)
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解析
ソフトウェア
名称: REFMAC / バージョン: 5.8.0135 / 分類: 精密化
CTF補正
タイプ: NONE
3次元再構成
解像度: 3.67 Å / 解像度の算出法: FSC 0.143 CUT-OFF / 粒子像の数: 263839 / 対称性のタイプ: POINT
精密化
解像度: 3.67→274.89 Å / Cor.coef. Fo:Fc: 0.801 / SU B: 22.557 / SU ML: 0.327 / ESU R: 0.213 / 立体化学のターゲット値: MAXIMUM LIKELIHOOD / 詳細: HYDROGENS HAVE BEEN ADDED IN THE RIDING POSITIONS
Rfactor
反射数
%反射
Rwork
0.4387
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-
obs
0.4387
880402
100 %
溶媒の処理
イオンプローブ半径: 0.8 Å / 減衰半径: 0.8 Å / VDWプローブ半径: 1.2 Å / 溶媒モデル: MASK