National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R00GM112982
米国
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
R35GM128777
米国
Damon Runyon Cancer Research Foundation
DFS-20-16
米国
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
1F30AI154907-01
米国
引用
ジャーナル: J Mol Biol / 年: 2022 タイトル: Role of Ring6 in the Function of the E. coli MCE Protein LetB. 著者: Casey Vieni / Nicolas Coudray / Georgia L Isom / Gira Bhabha / Damian C Ekiert / 要旨: LetB is a tunnel-forming protein found in the cell envelope of some double-membraned bacteria, and is thought to be important for the transport of lipids between the inner and outer membranes. In ...LetB is a tunnel-forming protein found in the cell envelope of some double-membraned bacteria, and is thought to be important for the transport of lipids between the inner and outer membranes. In Escherichia coli the LetB tunnel is formed from a stack of seven rings (Ring1 - Ring7), in which each ring is composed of a homo-hexameric assembly of MCE domains. The primary sequence of each MCE domain of the LetB protein is substantially divergent from the others, making each MCE ring unique in nature. The role of each MCE domain and how it contributes to the function of LetB is not well understood. Here we probed the importance of each MCE ring for the function of LetB, using a combination of bacterial growth assays and cryo-EM. Surprisingly, we find that ΔRing3 and ΔRing6 mutants, in which Ring3 and Ring6 have been deleted, confer increased resistance to membrane perturbing agents. Specific mutations in the pore-lining loops of Ring6 similarly confer increased resistance. A cryo-EM structure of the ΔRing6 mutant shows that despite the absence of Ring6, which leads to a shorter assembly, the overall architecture is maintained, highlighting the modular nature of MCE proteins. Previous work has shown that Ring6 is dynamic and in its closed state, may restrict the passage of substrate through the tunnel. Our work suggests that removal of Ring6 may relieve this restriction. The deletion of Ring6 combined with mutations in the pore-lining loops leads to a model for the tunnel gating mechanism of LetB. Together, these results provide insight into the functional roles of individual MCE domains and pore-lining loops in the LetB protein.
A: MCE family protein, Intermembrane transport protein YebT chimera B: MCE family protein, Intermembrane transport protein YebT chimera C: MCE family protein, Intermembrane transport protein YebT chimera D: MCE family protein, Intermembrane transport protein YebT chimera E: MCE family protein, Intermembrane transport protein YebT chimera F: MCE family protein, Intermembrane transport protein YebT chimera
モード: BRIGHT FIELD / 倍率(公称値): 37000 X / 最大 デフォーカス(公称値): 2200 nm / 最小 デフォーカス(公称値): 800 nm / Cs: 2.7 mm
試料ホルダ
試料ホルダーモデル: FEI TITAN KRIOS AUTOGRID HOLDER
撮影
平均露光時間: 1.5 sec. / 電子線照射量: 56.3 e/Å2 / フィルム・検出器のモデル: GATAN K3 (6k x 4k) / 撮影したグリッド数: 1 / 実像数: 10763 詳細: Images were collected in super resolution mode with a pixel size of 0.318A
画像スキャン
横: 11520 / 縦: 8184
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解析
ソフトウェア
名称: PHENIX / バージョン: 1.18.2_3874: / 分類: 精密化
EMソフトウェア
ID
名称
バージョン
カテゴリ
詳細
1
cryoSPARC
2.1
粒子像選択
Templatepicker
2
SerialEM
画像取得
4
CTFFIND
4.1
CTF補正
7
Coot
0.9
モデルフィッティング
9
PHENIX
1.18.2
モデル精密化
10
cryoSPARC
2.1
初期オイラー角割当
11
RELION
3.1.0
最終オイラー角割当
12
RELION
3.1.0
分類
13
RELION
3.1.0
3次元再構成
画像処理
詳細: Images were motion corrected in RELION 3.0
CTF補正
タイプ: PHASE FLIPPING AND AMPLITUDE CORRECTION
粒子像の選択
選択した粒子像数: 739130 詳細: Template picking followed by iterative rounds of 2D classification
対称性
点対称性: C6 (6回回転対称)
3次元再構成
解像度: 3.55 Å / 解像度の算出法: FSC 0.143 CUT-OFF / 粒子像の数: 39547 / 対称性のタイプ: POINT