Role of 4.5S RNA in Assembly of the Bacterial Signal Recognition Particle with Its Receptor

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Science  02 Jun 2000:
Vol. 288, Issue 5471, pp. 1640-1643
DOI: 10.1126/science.288.5471.1640

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The mechanism by which a signal recognition particle (SRP) and its receptor mediate protein targeting to the endoplasmic reticulum or to the bacterial plasma membrane is evolutionarily conserved. In Escherichia coli, this reaction is mediated by the Ffh/4.5S RNA ribonucleoprotein complex (Ffh/4.5S RNP; the SRP) and the FtsY protein (the SRP receptor). We have quantified the effects of 4.5S RNA on Ffh-FtsY complex formation by monitoring changes in tryptophan fluorescence. Surprisingly, 4.5S RNA facilitates both assembly and disassembly of the Ffh-FtsY complex to a similar extent. These results provide an example of an RNA molecule facilitating protein-protein interactions in a catalytic fashion.

  • * Present address: Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Medical School, 303 East Chicago Avenue, Chicago, IL 60611, USA.

  • To whom correspondence should be addressed. E-mail: walter{at}

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