The signal recognition particle (SRP) RNA links conformational changes in the SRP to protein targeting

Mol Biol Cell. 2007 Jul;18(7):2728-34. doi: 10.1091/mbc.e07-02-0117. Epub 2007 May 16.


The RNA component of the signal recognition particle (SRP) is universally required for cotranslational protein targeting. Biochemical studies have shown that SRP RNA participates in the central step of protein targeting by catalyzing the interaction of the SRP with the SRP receptor (SR). SRP RNA also accelerates GTP hydrolysis in the SRP.SR complex once formed. Using a reverse-genetic and biochemical analysis, we identified mutations in the E. coli SRP protein, Ffh, that abrogate the activity of the SRP RNA and cause corresponding targeting defects in vivo. The mutations in Ffh that disrupt SRP RNA activity map to regions that undergo dramatic conformational changes during the targeting reaction, suggesting that the activity of the SRP RNA is linked to the major conformational changes in the signal sequence-binding subunit of the SRP. In this way, the SRP RNA may coordinate the interaction of the SRP and the SR with ribosome recruitment and transfer to the translocon, explaining why the SRP RNA is an indispensable component of the protein targeting machinery.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Bacterial Proteins / metabolism
  • Catalysis
  • Escherichia coli / metabolism*
  • Escherichia coli Proteins / chemistry*
  • Escherichia coli Proteins / metabolism*
  • GTP Phosphohydrolases / metabolism
  • Guanosine Triphosphate / metabolism
  • Hydrolysis
  • Mutation / genetics
  • Protein Binding
  • Protein Structure, Secondary
  • Protein Structure, Tertiary
  • Protein Transport
  • RNA, Bacterial
  • RNA, Ribosomal / metabolism*
  • Receptors, Cytoplasmic and Nuclear / metabolism
  • Signal Recognition Particle / chemistry*
  • Signal Recognition Particle / metabolism*
  • Structure-Activity Relationship


  • 4.5S RNA
  • Bacterial Proteins
  • Escherichia coli Proteins
  • Ffh protein, E coli
  • FtsY protein, Bacteria
  • RNA, Bacterial
  • RNA, Ribosomal
  • Receptors, Cytoplasmic and Nuclear
  • Signal Recognition Particle
  • Guanosine Triphosphate
  • GTP Phosphohydrolases