Compaction of a prokaryotic signal-anchor transmembrane domain begins within the ribosome tunnel and is stabilized by SRP during targeting.
Compaction of a prokaryotic signal-anchor transmembrane domain begins within the ribosome tunnel and is stabilized by SRP during targeting.
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DOI：
10.1016/j.jmb.2012.07.023
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发表时间：
2012-11
影响因子：
5.6
通讯作者：
P. Robinson;J. Findlay;C. Woolhead
中科院分区：
文献类型：
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作者：
P. Robinson;J. Findlay;C. Woolhead
膜蛋白的共翻译靶向是由普遍保守的信号识别颗粒(SRP)介导的。在真核生物中，SRP在靶向翻译过程中减弱翻译；然而，在原核生物中，简化的SRP被认为在持续翻译期间进行靶向。在这里，我们展示了一个详细的逐步分析的目标，细菌三磷酸腺苷合成酶(F0c)的F0组分的亚基c到内膜。我们发现F0c的第一个跨膜(TM)信号锚定结构域在核糖体隧道的末端形成了一个紧凑的结构。这种结构是在与SRP相互作用之前形成的。在没有SRP的情况下，当TM结构域离开隧道时，这种结构会丢失；然而，在SRP的存在下，它是稳定的。我们的结果表明，原核生物SRP依赖的膜蛋白靶向途径的底物的早期蛋白质折叠与真核SRP靶向的不同。这些结果表明，早期通过靶向因子识别TM结构域可以确保膜靶向的效率保持不变。
Cotranslational targeting of membrane proteins is mediated by the universally conserved signal recognition particle (SRP). In eukaryotes, SRP attenuates translation during targeting; however, in prokaryotes, a simplified SRP is believed to carry out targeting during continuing translation. Here, we show a detailed stepwise analysis of the targeting of subunit c of the F0component of the bacterial ATP synthase (F0c) to the inner membrane. We show that the first transmembrane (TM) signal-anchor domain of F0c forms a compacted structure within the distal portion of the ribosome tunnel. This structure is formed just prior to the interaction with SRP. In the absence of SRP this structure is lost as the TM domain exits the tunnel; however in the presence of SRP it is stabilized. Our results suggest differences in early protein folding of substrates for prokaryotic SRP‐dependent membrane protein targeting pathways, from that of eukaryotic SRP targeting. These results imply that early TM domain recognition by targeting factors acts to ensure that the efficiency of membrane targeting is maintained.