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对脂质结构域标记物的荧光共振能量转移研究确定了半合成脂质化N-Ras在脂筏纳米结构域中的分配情况。

Study of Förster Resonance Energy Transfer to Lipid Domain Markers Ascertains Partitioning of Semisynthetic Lipidated N-Ras in Lipid Raft Nanodomains.

作者信息

Shishina Anna K, Kovrigina Elizaveta A, Galiakhmetov Azamat R, Rathore Rajendra, Kovrigin Evgenii L

机构信息

Chemistry Department, Marquette University , P.O. Box 1881, Milwaukee, Wisconsin 53201, United States.

出版信息

Biochemistry. 2018 Feb 6;57(5):872-881. doi: 10.1021/acs.biochem.7b01181. Epub 2018 Jan 10.

Abstract

Cellular membranes are heterogeneous planar lipid bilayers displaying lateral phase separation with the nanometer-scale liquid-ordered phase (also known as "lipid rafts") surrounded by the liquid-disordered phase. Many membrane-associated proteins were found to permanently integrate into the lipid rafts, which is critical for their biological function. Isoforms H and N of Ras GTPase possess a unique ability to switch their lipid domain preference depending on the type of bound guanine nucleotide (GDP or GTP). This behavior, however, has never been demonstrated in vitro in model bilayers with recombinant proteins and therefore has been attributed to the action of binding of Ras to other proteins at the membrane surface. In this paper, we report the observation of the nucleotide-dependent switch of lipid domain preferences of the semisynthetic lipidated N-Ras in lipid raft vesicles in the absence of additional proteins. To detect segregation of Ras molecules in raft and disordered lipid domains, we measured Förster resonance energy transfer between the donor fluorophore, mant, attached to the protein-bound guanine nucleotides, and the acceptor, rhodamine-conjugated lipid, localized into the liquid-disordered domains. Herein, we established that N-Ras preferentially populated raft domains when bound to mant-GDP, while losing its preference for rafts when it was associated with a GTP mimic, mant-GppNHp. At the same time, the isolated lipidated C-terminal peptide of N-Ras was found to be localized outside of the liquid-ordered rafts, most likely in the bulk-disordered lipid. Substitution of the N-terminal G domain of N-Ras with a homologous G domain of H-Ras disrupted the nucleotide-dependent lipid domain switch.

摘要

细胞膜是异质的平面脂质双层,呈现出横向相分离,其中纳米级的液相有序相(也称为“脂筏”)被液相无序相所包围。许多膜相关蛋白被发现可永久整合到脂筏中,这对其生物学功能至关重要。Ras GTP酶的同工型H和N具有独特的能力,可根据结合的鸟嘌呤核苷酸(GDP或GTP)的类型来切换其脂质结构域偏好。然而,这种行为从未在含有重组蛋白的模型双层中体外得到证实,因此被归因于Ras与膜表面其他蛋白结合的作用。在本文中,我们报告了在没有其他蛋白的情况下,观察到半合成脂化的N-Ras在脂筏囊泡中脂质结构域偏好的核苷酸依赖性切换。为了检测Ras分子在筏状和无序脂质结构域中的分离,我们测量了连接到与蛋白结合的鸟嘌呤核苷酸上的供体荧光团mant与定位在液相无序结构域中的受体罗丹明偶联脂质之间的Förster共振能量转移。在此,我们确定N-Ras与mant-GDP结合时优先分布在筏状结构域中,而当它与GTP类似物mant-GppNHp结合时则失去了对脂筏的偏好。同时,发现N-Ras分离的脂化C末端肽位于液相有序脂筏之外,很可能在大量无序脂质中。用H-Ras的同源G结构域替换N-Ras的N末端G结构域破坏了核苷酸依赖性脂质结构域切换。

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