Structures of SRP54 and SRP19, the Two Proteins that Organize the Ribonucleic Core of the Signal Recognition Particle from Pyrococcus furiosus (original) (raw)
Figure 4
Conformational variability of the different Ffh/SRP54 proteins.
(A) and (B) Conformational variability of the linker in the Ffh/SRP54 GTPases. (A) Superposition of the _Pfu_- and _Ssol_- free SRP54 structures. The NG domains (in grey) have been superposed to emphasize the different conformation adopted by the M domains (in red) and the G to M linkers (in yellow). The C terminal helices α7 of the G domains are highlighted (in pink). (B) Superposition of the _Pfu_-SRP54 and the _Mja_-SRP emphasizing the clash between the _Mja_-SRP RNA•SRP19 and the _Pfu_-M domain. In both figures _Pfu_-SRP54 is shown in the same orientation. The position of the glycine residues acting as “pivot points” is indicated with a red asterisk. (C) and (D) Conformational changes in the M domain. (C) The _Pfu_-M domain is shown superposed with the M domain as observed in the Ec, Taq and Mja structures. (D) The _Pfu_-M domain is superposed with the _Ssol_-M domain. As a reference the backbones of the SRP RNA from Ec, Mja and Ssol are shown in white. α helices are labeled according to the secondary structure assignment of _Pfu_-SRP54. The arrows emphasize the rearrangement and shift in position for the helix α10 when Taq, Ssol and Pfu structures are compared. In both figures the _Pfu_-M domain is shown in the same orientation.