Signal peptides bind and aggregate RNA - An alternative explanation for GTPase inhibition in the signal recognition particle
Signal peptides bind and aggregate RNA - An alternative explanation for GTPase inhibition in the signal recognition particle
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DOI：
10.1074/jbc.m011128200
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发表时间：
2001-04-13
影响因子：
4.8
通讯作者：
Gierasch, LM
中科院分区：
文献类型：
--
作者：
Swain, JF;Gierasch, LM
N端信号序列通过与信号识别颗粒相互作用，可以将新生蛋白质链引导至原核生物的内膜和真核生物的内质网。在这项研究中，我们表明，分离的肽对应于几种细菌信号序列抑制大肠杆菌信号识别颗粒的GT3活性，如以前报道的（米勒，J.D.，伯恩斯坦，H. D、和Waiter，P.（1994）Nature 367，657-659），但不是通过提出的直接机制。相反，分离的信号肽非特异性地与RNA组分结合，并聚集整个信号识别颗粒，导致其固有的GT3活性丧失。令人惊讶的是，只有“功能性”肽序列聚集RNA;通常用作“非功能性”阴性对照的肽（例如在疏水核内具有缺失或带电取代的那些）在物理特性上充分不同，使得它们不聚集RNA，因此对信号识别颗粒的GTdR活性没有影响。我们建议，功能性信号肽对信号识别颗粒的GTdR活性的影响是这些体外研究中使用的高肽浓度和低盐条件的人工产物，并且在新生链的N末端的信号序列在体内不表现出这种活性。
N-terminal signal sequences can direct nascent protein chains to the inner membrane of prokaryotes and the endoplasmic reticulum of eukaryotes by interacting with the signal recognition particle. In this study, we show that isolated peptides corresponding to several bacterial signal sequences inhibit the GTPase activity of the Escherichia coli signal recognition particle, as previously reported (Miller, J. D., Bernstein, H. D., and Waiter, P. (1994) Nature 367, 657-659), but not by the direct mechanism proposed. Instead, isolated signal peptides bind nonspecifically to the RNA component and aggregate the entire signal recognition particle, leading to a loss of its intrinsic GTPase activity. Surprisingly, only "functional" peptide sequences aggregate RNA;the peptides in general use as "nonfunctional" negative controls (e.g. those with deletions or charged substitutions within the hydrophobic core), are sufficiently different in physical character that they do not aggregate RNA and thus have no effect on the GTPase activity of the signal recognition particle. We propose that the reported effect of functional signal peptides on the GTPase activity of the signal recognition particle is an artifact of the high peptide concentrations and low salt conditions used in these in vitro studies and that signal sequences at the N terminus of nascent chains in vivo do not exhibit this activity.