定义外膜蛋白OMP.ppt

Making a beta-barrel: assembly of outer membrane proteins in Gram-negative bacteria
报告人:王泽焕

What is the OMP?
细菌表面蛋白与外膜蛋白的区别?
革兰氏阴性菌与革兰阳性菌相比较其细胞壁有一种特殊成分叫外膜。外膜由内到外由脂蛋白、脂质双层和脂多糖三部分组成,脂质双层内镶嵌的蛋白质称为外膜蛋白。
某些革兰氏阳性菌表面有一些特殊的表面蛋白;如金黄色葡萄球菌的A蛋白,A链球菌的M蛋白等。
定义:外膜蛋白(OMP)是革兰氏阴性菌特有的,存在于外
膜之中及与外膜有关的所有蛋白的总称。
What is the OMP?
What is the OMP?
外膜蛋白的结构
外膜蛋白不是由跨生物膜的α螺旋组成,而是由反平行的β桶结构组成,不同的外膜蛋白的β-桶由不同偶数个β-折叠片组成,从8个到22个不等。
外膜蛋白的功能
外膜蛋白能使革兰氏阴性菌抵抗恶劣环境,与此
同时,镶嵌蛋白大部分与细菌细胞的关键功能起到作用。
What is the OMP?
An OMP is born!
The OMP assembly pathway in E. coli . Outer membrane proteins (OMPs) are synthesized as unfolded precursors in the cytoplasm and translocated across the inner membrane (IM) via the Sec translocase. Once in the periplasm, chaperones recognize unfolded OMPs and prevent them from forming misfolded aggregates. The multi-subunit plex folds and inserts OMPs into the outer membrane
Synthesize as pre-proteins
with an N-terminal signal sequence
An OMP is born!
i DP, Silhavy TJ. Biochim Biophys Acta 2011.
only unfolded proteins can be modated by the Sec pathway
The Sec pathway is responsible for
transporting the bulk of all exported proteins in E. coli
a targeting element that routes proteins to specific protein translocases embedded in the IM
The Sec pathway
Sec translocase(Sec 转运酶)
Sec转运酶是一个多组分的蛋白质复合体,膜蛋白三聚体 SecYEG 及水解ATP的动力蛋白 SecA 构成 Sec 转运酶的核心。整合膜蛋白 SecD,SecF 和 YajC 形成了一个复合体亚单位,可与 SecYEG 相连并稳定SecA蛋白的膜结合形式。
SecYEG——转运通道
SecA——亲水蛋白质,具有ATP 酶活性,是Sec蛋白质转运途径中的“动力泵”
SecG——小分子的具有柔性膜蛋白
SecB——疏水的表面和新合成的多肽结合
Anastassios E. Federation of European Biochemical Societies , 2000, 476 : 18 − 21.
Sugai R, Takemae K, Tokuda H. J Biol Chem , 2007, 282 (40), 29540 − 29548.
Note: some preproteins are delivered to SecA via SecB, while others directly interact with SecA without the participation of SecB. Upon interacting with the inner membranebound SecYEG, SecA may or may not dissociate to monomer.
Fig. 1 Schematic representation of the E. coli Sec transport system
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