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首页> 外文期刊>Biochemistry >Regulation of Signal Peptidase by Phospholipids in Membrane:Characterization of Phospholipid Bilayer Incorporated Escherichia coli Signal Peptidase
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Regulation of Signal Peptidase by Phospholipids in Membrane:Characterization of Phospholipid Bilayer Incorporated Escherichia coli Signal Peptidase

机译：膜中磷脂对信号肽酶的调节：结合磷脂双分子层的大肠杆菌信号肽酶的表征

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摘要

Prokaryotic signal peptidases are membrane-bound enzymes.They cleave signal petpides from precursors of secretary proteins.To study the enzyme in its natural environment,which is phospholipid bilayers,we developed a method that allows us effectively to incorporate full-length Escherichia coli signal peptidase I into phospholipid vesicles.The membrane-bound signal peptidase showed high activity on a designed substrate.The autolysis site of the enzyme is separated from its catalytic site in vesicles by the lipid bilayer,resulting in a dramatic decrease of the autolysis rate.Phosphotidylethanolamine,which is the most abundant lipid in Escherichia coli inner membrane,is required to maintain activity of the membrane-incorporated signal peptidase.The maximal activity is achieved at about 55% phosphotidylethanolamine.Negatively charged lipids,which are also abundant in Escherichia coli inner membrane,enhances the activity of the enzyme too.Its mechanism,however,cannot be fully explained by its ability to increase the affinity of the substrate to the membrane.A reaction mechanism was developed based on the observaton that cleavage only takes place when the enzyme and the substrate are bound to the same vesicle.Accordingly,a kinetic analysis is presented to explain some of the unique features of phospholipid vesicles incorporated signal peptidase,including the effect of lipid concentration and substrate-vesicle interaction.
机译：原核信号肽酶是膜结合酶，它们从秘书蛋白的前体中裂解信号肽。为了研究天然环境中的酶（磷脂双层），我们开发了一种方法，该方法可有效整合全长的大肠杆菌信号肽酶。 I进入磷脂囊泡，膜结合信号肽酶在设计的底物上显示高活性，该酶的自溶位点通过脂质双层与囊泡中的催化位点分开，导致自溶速率急剧降低。它是大肠杆菌内膜中最丰富的脂质，是维持膜结合的信号肽酶活性所必需的。在约55％的磷脂酰乙醇胺中可达到最大活性。带负电荷的脂质在大肠杆菌内膜中也很丰富，增强酶的活性。但是其机理尚不能完全解释。基于这种观察，开发了一种反应机理，即只有当酶和底物结合在同一囊泡上时才发生裂解。因此，进行了动力学分析以解释一些反应机理。结合信号肽酶的磷脂囊泡的独特功能，包括脂质浓度和底物-囊泡相互作用的影响。

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