ジャーナル: Nat Commun / 年: 2023 タイトル: Molecular mechanism of phospholipid transport at the bacterial outer membrane interface. 著者: Jiang Yeow / Min Luo / Shu-Sin Chng / 要旨: The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer with outer leaflet lipopolysaccharides and inner leaflet phospholipids (PLs). This unique lipid asymmetry renders the ...The outer membrane (OM) of Gram-negative bacteria is an asymmetric lipid bilayer with outer leaflet lipopolysaccharides and inner leaflet phospholipids (PLs). This unique lipid asymmetry renders the OM impermeable to external insults, including antibiotics and bile salts. To maintain this barrier, the OmpC-Mla system removes mislocalized PLs from the OM outer leaflet, and transports them to the inner membrane (IM); in the first step, the OmpC-MlaA complex transfers PLs to the periplasmic chaperone MlaC, but mechanistic details are lacking. Here, we biochemically and structurally characterize the MlaA-MlaC transient complex. We map the interaction surfaces between MlaA and MlaC in Escherichia coli, and show that electrostatic interactions are important for MlaC recruitment to the OM. We further demonstrate that interactions with MlaC modulate conformational states in MlaA. Finally, we solve a 2.9-Å cryo-EM structure of a disulfide-trapped OmpC-MlaA-MlaC complex in nanodiscs, reinforcing the mechanism of MlaC recruitment, and highlighting membrane thinning as a plausible strategy for directing lipids for transport. Our work offers critical insights into retrograde PL transport by the OmpC-Mla system in maintaining OM lipid asymmetry.
名称: Outer membrane porin C / タイプ: complex / ID: 2 / 親要素: 1 / 含まれる分子: #1 詳細: Trimeric OmpC porins in complex with MlaA at the outer membrane disulfide-trapped with MlaC
フィルム・検出器のモデル: GATAN K3 (6k x 4k) / デジタル化 - サイズ - 横: 5760 pixel / デジタル化 - サイズ - 縦: 4092 pixel / 撮影したグリッド数: 1 / 実像数: 6018 / 平均露光時間: 5.99 sec. / 平均電子線量: 90.0 e/Å2 詳細: Images were collected in movie-mode at 50 frames per image
実験機器
モデル: Titan Krios / 画像提供: FEI Company
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画像解析
粒子像選択
選択した数: 2434319 詳細: We performed automated particle picking using Blob and Template Picker for initial template picking and final sampling respectively.
初期モデル
モデルのタイプ: NONE
初期 角度割当
タイプ: MAXIMUM LIKELIHOOD / ソフトウェア - 名称: cryoSPARC (ver. 4.0.0)
最終 3次元分類
クラス数: 3 / ソフトウェア - 名称: cryoSPARC (ver. 4.0.0)
最終 角度割当
タイプ: MAXIMUM LIKELIHOOD / ソフトウェア - 名称: cryoSPARC (ver. 4.0.0)