A cleavable N-terminal membrane anchor is involved in membrane binding of the Escherichia coli SRP receptor
A cleavable N-terminal membrane anchor is involved in membrane binding of the Escherichia coli SRP receptor
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DOI：
10.1016/j.jmb.2008.01.040
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发表时间：
2008-03-28
影响因子：
5.6
通讯作者：
Koch, Hans-Georg
中科院分区：
文献类型：
--
作者：
Weiche, Benjamin;Buerk, Jonas;Koch, Hans-Georg
与真核生物不同，细菌信号识别颗粒(SRP)受体缺乏膜连接的SRP受体(SR)β亚基，仅由SRα同源物FtsY FtsY组成，是由三个结构域组成的模块化蛋白。FtsY的N-和G-结构域与FFH/SRP54和SRα的相应结构域高度相似，构成了FtsY的核心。相反，弱保守的N-末端A-结构域似乎不是必需的，其确切功能尚不清楚。我们的数据表明，在A-结构域的N-末端有一个14个氨基酸长的正电区参与了FtsY-SecYEG相互作用的稳定。突变分析表明，带正电荷的残基对这一功能至关重要，我们认为14个氨基酸区域作为瞬时脂质锚。在没有它的情况下，FtsY支持共翻译整合的活性减少到约50%。引人注目的是，在活体中，存在一种截短的FtsY亚型，它恰好缺少这14个氨基酸。与主要与膜共分的全长FtsY不同，N末端截短的异构体主要存在于可溶部分中。在第14位突变保守的甘氨酸残基可以阻止截短的异构体的形成，并损害FtsY在共翻译靶向中的活性。这些数据表明，FtsY的膜结合和功能在一定程度上是由保守的14个氨基酸基序的蛋白水解性切割调节的。(C)2008爱思唯尔有限公司。保留所有权利。
Different from eukaryotes, the bacterial signal recognition particle (SRP) receptor lacks a membrane-tethering SRP receptor (SR) beta subunit and is composed of only the SR alpha homologue FtsY FtsY is a modular protein composed of three domains. The N- and G-domains of FtsY are highly similar to the corresponding domains of Ffh/SRP54 and SR alpha and constitute the essential core of FtsY. In contrast, the weakly conserved N-terminal A-domain does not seem to be essential, and its exact function is unknown. Our data show that a 14-amino-acid-long positively charged region at the N-terminus of the A-domain is involved in stabilizing the FtsY-SecYEG interaction. Mutant analyses reveal that the positively charged residues are crucial for this function, and we propose that the 14-amino-acid region serves as a transient lipid anchor. In its absence, the activity of FtsY to support cotranslational integration is reduced to about 50%. Strikingly, in vivo, a truncated isoform of FtsY that lacks exactly these first 14 amino acids exists. Different from full-length FtsY, which primarily cofractionates with the membrane, the N-terminally truncated isoform is primarily present in the soluble fraction. Mutating the conserved glycine residue at position 14 prevents the formation of the truncated isoform and impairs the activity of FtsY in cotranslational targeting. These data suggest that membrane binding and function of FtsY are in part regulated by proteolytic cleavage of the conserved 14-amino-acid motif. (C) 2008 Elsevier Ltd. All rights reserved.