Activated GTPase movement on an RNA scaffold drives co-translational protein targeting

Kuang Shen, Sinan Arslan, David Akopian, Taekjip Ha, Shu Ou Shan

Research output: Contribution to journalArticle

Abstract

Approximately one-third of the proteome is initially destined for the eukaryotic endoplasmic reticulum or the bacterial plasma membrane. The proper localization of these proteins is mediated by a universally conserved protein-targeting machinery, the signal recognition particle (SRP), which recognizes ribosomes carrying signal sequences and, through interactions with the SRP receptor, delivers them to the protein-translocation machinery on the target membrane. The SRP is an ancient ribonucleoprotein particle containing an essential, elongated SRP RNA for which precise functions have remained elusive. Here we used single-molecule fluorescence microscopy to show that the Escherichia coli SRP-SRP receptor GTPase complex, after initial assembly at the tetraloop end of SRP RNA, travels over 100Å to the distal end of this RNA, where rapid GTP hydrolysis occurs. This movement is negatively regulated by the translating ribosome and, at a later stage, positively regulated by the SecYEG translocon, providing an attractive mechanism for ensuring the productive exchange of the targeting and translocation machineries at the ribosome exit site with high spatial and temporal accuracy. Our results show that large RNAs can act as molecular scaffolds that enable the easy exchange of distinct factors and precise timing of molecular events in a complex cellular process; this concept may be extended to similar phenomena in other ribonucleoprotein complexes.

Original languageEnglish (US)
Pages (from-to)271-275
Number of pages5
JournalNature
Volume492
Issue number7428
DOIs
StatePublished - Dec 13 2012

ASJC Scopus subject areas

  • General

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    Shen, K., Arslan, S., Akopian, D., Ha, T., & Shan, S. O. (2012). Activated GTPase movement on an RNA scaffold drives co-translational protein targeting. Nature, 492(7428), 271-275. https://doi.org/10.1038/nature11726