Structure of the GMPPNP-stabilized NG domain complex of the SRP GTPases Ffh and FtsY

Joseph Gawronski-Salerno, Douglas M. Freymann*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

23 Scopus citations


Ffh and FtsY are GTPase components of the signal recognition particle co-translational targeting complex that assemble during the SRP cycle to form a GTP-dependent and pseudo twofold symmetric heterodimer. Previously the SRP GTPase heterodimer has been stabilized and purified for crystallographic studies using both the non-hydrolysable GTP analog GMPPCP and the pseudo-transition state analog GDP:AlF4, revealing in both cases a buried nucleotide pair that bridges and forms a key element of the heterodimer interface. A complex of Ffh and FtsY from Thermus aquaticus formed in the presence of the analog GMPPNP could not be obtained, however. The origin of this failure was previously unclear, and it was thought to have arisen from either instability of the analog, or, alternatively, from differences in its interactions within the tightly conscribed composite active site chamber of the complex. Using insights gained from the previous structure determinations, we have now determined the structure of the SRP GTPase targeting heterodimer stabilized by the non-hydrolysable GTP analog GMPPNP. The structure demonstrates how the different GTP analogs are accommodated within the active site chamber despite slight differences in the geometry of the phosphate chain. It also reveals a K+ coordination site at the highly conserved DARGG loop at the N/G interdomain interface.

Original languageEnglish (US)
Pages (from-to)122-128
Number of pages7
JournalJournal of Structural Biology
Issue number1
StatePublished - Apr 2007
Externally publishedYes


  • Complex assembly
  • Ffh
  • FtsY
  • GTPase
  • GppNHp
  • SRP
  • X-ray crystallography

ASJC Scopus subject areas

  • Structural Biology


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