Induced structural changes of 7SL RNA during the assembly of human signal recognition particle

Nat Struct Biol. 2002 Oct;9(10):740-4. doi: 10.1038/nsb843.


The eukaryotic signal recognition particle (SRP) is a cytoplasmic ribonucleoprotein particle that targets secretory and membrane proteins to the endoplasmic reticulum. The binding of SRP54 to the S domain of 7SL RNA is highly dependent on SRP19. Here we present the crystal structure of a human SRP ternary complex consisting of SRP19, the M domain of SRP54 and the S domain of 7SL RNA. Upon binding of the M domain of SRP54 to the 7SL RNA-SRP19 complex, the asymmetric loop of helix 8 in 7SL RNA collapses. The bases of the four nucleotides in the long strand of the asymmetric loop continuously stack and interact with the M domain, whereas the two adenines in the short strand flip out and form two A-minor motifs with helix 6. This stabilizing interaction is only possible when helix 6 has been positioned parallel to helix 8 by the prior binding of SRP19 to the tetraloops of helices 6 and 8. Hence, the crystal structure of the ternary complex suggests why SRP19 is necessary for the stable binding of SRP54 to the S domain RNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Base Sequence
  • Cloning, Molecular
  • Crystallography, X-Ray
  • Escherichia coli
  • Humans
  • Macromolecular Substances
  • Molecular Sequence Data
  • Protein Conformation
  • RNA, Small Cytoplasmic / chemistry*
  • RNA, Small Cytoplasmic / metabolism
  • Recombinant Proteins / chemistry
  • Recombinant Proteins / metabolism
  • Saccharomyces cerevisiae Proteins*
  • Sequence Alignment
  • Signal Recognition Particle / chemistry*
  • Signal Recognition Particle / metabolism


  • 7SL RNA
  • Macromolecular Substances
  • RNA, Small Cytoplasmic
  • Recombinant Proteins
  • SRP19 protein, human
  • SRP54 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Signal Recognition Particle

Associated data

  • PDB/1MFQ