X-ray Structures of the Signal Recognition Particle Receptor Reveal Targeting Cycle Intermediates
Figure 5
The N-terminal helix N1 packs against the nucleotide-specifying motif IV.
The structures of FtsY in (A) apo form, (B) monomeric GMPPNP-bound form, (C) GMPPCP-bound form from the targeting complex with Ffh, and (D) monomeric GDP-bound form were aligned based on the P-loop; the N-domain (blue) and G-domain (green) are highlighted. In the structures of apo and GMPPNP-bound FtsY the N-terminal helix, N1 (cyan), extends into the N-domain and packs against the conserved GTPase motif IV which positions the nucleotide-specifying Asp258 to interact with the nucleotide. The α4 helix (yellow) anchors the interface between the N and G domains. The C-terminal helix, αC (red), which along with N1 pack together at the N/G interface, is observed in a similar arrangement in the three monomeric forms (A, B, D) but rearranges in the complex form of FtsY (C).