Structural basis of signal sequence surveillance and selection by the SRP-FtsY complex

Ottilie Von Loeffelholz, Kèvin Knoops, Aileen Ariosa, Xin Zhang, Manikandan Karuppasamy, Karine Huard, Guy Schoehn, Imre Berger, Shu Ou Shan, Christiane Schaffitzel

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Signal-recognition particle (SRP)-dependent targeting of translating ribosomes to membranes is a multistep quality-control process. Ribosomes that are translating weakly hydrophobic signal sequences can be rejected from the targeting reaction even after they are bound to the SRP. Here we show that the early complex, formed by Escherichia coli SRP and its receptor FtsY with ribosomes translating the incorrect cargo EspP, is unstable and rearranges inefficiently into subsequent conformational states, such that FtsY dissociation is favored over successful targeting. The N-terminal extension of EspP is responsible for these defects in the early targeting complex. The cryo-electron microscopy structure of this 'false' early complex with EspP revealed an ordered M domain of SRP protein Ffh making two ribosomal contacts, and the NG domains of Ffh and FtsY forming a distorted, flexible heterodimer. Our results provide a structural basis for SRP-mediated signal-sequence selection during recruitment of the SRP receptor.

Original languageEnglish (US)
Pages (from-to)604-610
Number of pages7
JournalNature Structural and Molecular Biology
Issue number5
StatePublished - May 2013

All Science Journal Classification (ASJC) codes

  • Structural Biology
  • Molecular Biology


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