Figure 4. Low-resolution cryo-EM structure of the 30S·ABCE1 post-splitting complex.

(a) Overview of the 30S·ABCE1 post-splitting complex electron density map low-pass filtered at ∼25 Å. The final 30S·ABCE1 data set contained 19,500 particles and the final resolution was 17 Å (Fourier shell correlation 0.5). The ABCE1 extra density is shown in red. (b) Model of the 30S·ABCE1 complex in post-splitting state showing the models of the P. furiosus small 30S subunit (grey; 4V6U)⁵² and ribosome-bound ABCE1 (FeS cluster domain brown; NBD1 orange and NBD2 yellow; hinges 1 and 2 green, ADP-bound green; 3J15)⁸. The FeS cluster domain was fitted into the extra density located near ribosomal proteins S12 (purple). (c) Zoom-in showing the pre-splitting (wheat) and post-splitting (brown) state of the FeS cluster domain. The post-splitting state was modelled based on a specific inter-crosslink in XL-MS between lysine 60 of ABCE1 (lysine 64 in P. furiosus) and lysine 40 of S12 (shown in red). Because of this conformation change, the Cα–Cα distance between these highly conserved lysines in Archaea, yeast and human is reduced from 59.5 Å in the pre-splitting state to 17.5 Å in the post-splitting state.