期刊
NATURE
卷 492, 期 7428, 页码 271-+出版社
NATURE PUBLISHING GROUP
DOI: 10.1038/nature11726
关键词
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资金
- National Institutes of Health (NIH) [GM078024, GM45162, GM065367]
- Caltech [350270]
- Beckman Young Investigator award
- David and Lucile Packard Fellowship in Science and Engineering
- Henry Dreyfus Teacher-Scholar award
- National Science Foundation Physics Frontiers Centers program [08222613]
Approximately one-third of the proteome is initially destined for the eukaryotic endoplasmic reticulum or the bacterial plasma membrane(1). 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(2-4) and, through interactions with the SRP receptor(5,6), delivers them to the protein-translocation machinery on the target membrane(7). 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 tetra-loop end of SRP RNA, travels over 100 angstrom 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.
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