Topology of SREBP cleavage-activating protein, a polytopic membrane protein with a sterol-sensing domain
Topology of SREBP cleavage-activating protein, a polytopic membrane protein with a sterol-sensing domain
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DOI：
10.1074/jbc.273.27.17243
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发表时间：
1998-07-03
影响因子：
4.8
通讯作者：
Goldstein, JL
中科院分区：
文献类型：
--
作者：
Nohturfft, A;Brown, MS;Goldstein, JL
固醇调节元件结合蛋白(SREBPs)的NH2末端片段由内质网膜蛋白释放出来，其活性依赖于SREBP裂解激活蛋白(SCAP)，SREBP是一种多位的内质网膜蛋白。SCAP的活性被似乎与SCAP的多位膜结构域相互作用的甾醇抑制。在这里，我们使用蛋白酶保护和N-连接的糖基化定位技术来定义SCAP的八个跨膜结构域的拓扑结构，数据表明SCAP的NH、末端和COOH末端面对胞浆，跨膜片段I和7糖基化后的长管腔内环，证实了它们的管腔位置。由膜跨段2-6组成的区域与其他三种蛋白质中可能的类固醇敏感结构域序列相似：3-羟基-3-甲基戊二酰辅酶A还原酶(HMG-CoA还原酶)，Niemann-Pick CI蛋白，以及形态原受体补丁。SCAP中八个膜跨段的取向与HMG-CoA还原酶(Olender，E，H，和Simoni，R.D.，(1992)J.Biol)提出的模型一致。化学。267,4223-4235)，SCAP和HMG-CoA还原酶的跨膜结构域使这两个分子的功能活性对甾醇敏感。这两种蛋白质的共同膜拓扑结构与甾醇通过共同机制调节这两种蛋白质的概念是一致的。
The NH2-terminal fragments of sterol regulatory element-binding proteins (SREBPs) are released from endoplasmic reticulum membranes by proteases whose activities depend upon SREBP cleavage-activating protein (SCAP), a polytopic endoplasmic reticulum membrane protein. The activity of SCAP is inhibited by sterols, which appear to interact with the polytopic membrane domain of SCAP. Here, we use protease protection and N-linked glycosylation site-mapping techniques to define the topology of the eight membrane-spanning domains of SCAP, The data indicate that the NH,terminus and COOH terminus of SCAP face the cytosol, The long intralumenal loops after membrane-spanning segments I and 7 are glycosylated, confirming their lumenal location. The region comprising membrane-spanning segments 2-6 shows sequence resemblance to putative sterol-sensing domains in three other proteins: 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoA reductase), the Niemann-Pick CI protein, and the morphogen receptor Patched. The orientation of the eight membrane-spanning segments in SCAP is consistent with the model proposed for HMG-CoA reductase (Olender, E, H,, and Simoni, R. D, (1992) J. Biol. Chem. 267, 4223-4235), The membrane-spanning domains of SCAP and HMG-CoA reductase confer sterol sensitivity upon the functional activities of the two molecules. The common membrane topology of the two proteins is consistent with the notion that sterols regulate both proteins by a common mechanism.