Skip to main content
. Author manuscript; available in PMC: 2008 Jun 1.
Published in final edited form as: J Mol Biol. 2007 Mar 20;369(2):512–524. doi: 10.1016/j.jmb.2007.03.032

Figure 1.

Figure 1

The signal recognition particle (SRP). (A) Architecture of the mammalian SRP. SRP proteins are shown as colored and gray ovals; the RNA is yellow. (B) ‘SRP54-late’ model for cellular assembly of the mammalian SRP. Five of six SRP proteins (SRP9, SRP14, SRP19, SRP68, and SRP72) (gray and green ovals) enter the nucleus or nucleolus to assemble with the SRP RNA. The partially assembled complex is then transported back into the cytoplasm to bind SRP54 (purple) and form the native SRP holocomplex. (C) In vitro scheme for native SRP19-SRP54-SRP RNA ternary complex formation via the SRP54-late assembly pathway. (D) ‘SRP54-early’ pathway that leads to formation of a non-native ternary complex, termed the non-compartmentalized complex, in which two RNA binding loops in SRP19 do not fold to their native conformation.10 (E) Three-fold protein-RNA interface in the native SRP ternary complex. SRP19 loop 2 (gray) is positioned in a cleft formed by SRP54 and the RNA. The figure shows the same complex20 as panel C, but has been rotated ~90° to afford a view from the ‘top’ of the three-component interface.