National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
R01AI081059
米国
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
F32GM108258
米国
National Institutes of Health/National Institute of General Medical Sciences (NIH/NIGMS)
F31GM116210
米国
Howard Hughes Medical Institute (HHMI)
米国
引用
ジャーナル: Nature / 年: 2020 タイトル: Structure of a nascent membrane protein as it folds on the BAM complex. 著者: David Tomasek / Shaun Rawson / James Lee / Joseph S Wzorek / Stephen C Harrison / Zongli Li / Daniel Kahne / 要旨: Mitochondria, chloroplasts and Gram-negative bacteria are encased in a double layer of membranes. The outer membrane contains proteins with a β-barrel structure. β-Barrels are sheets of β-strands ...Mitochondria, chloroplasts and Gram-negative bacteria are encased in a double layer of membranes. The outer membrane contains proteins with a β-barrel structure. β-Barrels are sheets of β-strands wrapped into a cylinder, in which the first strand is hydrogen-bonded to the final strand. Conserved multi-subunit molecular machines fold and insert these proteins into the outer membrane. One subunit of the machines is itself a β-barrel protein that has a central role in folding other β-barrels. In Gram-negative bacteria, the β-barrel assembly machine (BAM) consists of the β-barrel protein BamA, and four lipoproteins. To understand how the BAM complex accelerates folding without using exogenous energy (for example, ATP), we trapped folding intermediates on this machine. Here we report the structure of the BAM complex of Escherichia coli folding BamA itself. The BamA catalyst forms an asymmetric hybrid β-barrel with the BamA substrate. The N-terminal edge of the BamA catalyst has an antiparallel hydrogen-bonded interface with the C-terminal edge of the BamA substrate, consistent with previous crosslinking studies; the other edges of the BamA catalyst and substrate are close to each other, but curl inward and do not pair. Six hydrogen bonds in a membrane environment make the interface between the two proteins very stable. This stability allows folding, but creates a high kinetic barrier to substrate release after folding has finished. Features at each end of the substrate overcome this barrier and promote release by stepwise exchange of hydrogen bonds. This mechanism of substrate-assisted product release explains how the BAM complex can stably associate with the substrate during folding and then turn over rapidly when folding is complete.
全体 : BamABCDE bound to substrate BamA with loop 1 deleted
全体
名称: BamABCDE bound to substrate BamA with loop 1 deleted
要素
複合体: BamABCDE bound to substrate BamA with loop 1 deleted
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超分子 #1: BamABCDE bound to substrate BamA with loop 1 deleted
超分子
名称: BamABCDE bound to substrate BamA with loop 1 deleted タイプ: complex / ID: 1 / 親要素: 0 / 含まれる分子: #1 詳細: contains a cysteine crosslink between S439C in BamA and E800C in the substrate
由来(天然)
生物種: Escherichia coli K-12 (大腸菌)
組換発現
生物種: Escherichia coli BL21(DE3) (大腸菌)
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実験情報
-
構造解析
手法
クライオ電子顕微鏡法
解析
単粒子再構成法
試料の集合状態
particle
-
試料調製
濃度
5 mg/mL
緩衝液
pH: 8 構成要素:
濃度
式
名称
20.0 mM
Tris-HCl
tris(hydroxymethyl)aminomethane hydrochloride
150.0 mM
NaCl
sodium chloride
0.02 %
GDN
glyco-diosgenin
グリッド
詳細: unspecified
凍結
凍結剤: ETHANE / チャンバー内湿度: 100 % / チャンバー内温度: 298 K / 装置: FEI VITROBOT MARK IV
詳細
contains a cysteine crosslink between S439C in BamA and E800C in the substrate