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Heuer, Andre; Gerovac, Milan; Schmidt, Christian; Trowitzsch, Simon; Preis, Anne; Kötter, Peter; Berninghausen, Otto; Becker, Thomas; Beckmann, Roland; Tampe, Robert (2017): Structure of the 40S-ABCE1 post-splitting complex in ribosome recycling and translation initiation. In: Nature Structural & Molecular Biology, Vol. 24, No. 5: pp. 453-460
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Abstract

The essential ATP-binding cassette protein ABCE1 splits 80S ribosomes into 60S and 40S subunits after canonical termination or quality-control-based mRNA surveillance processes. However, the underlying splitting mechanism remains enigmatic. Here, we present a cryo-EM structure of the yeast 40S-ABCE1 post-splitting complex at 3.9-angstrom resolution. Compared to the pre-splitting state, we observe repositioning of ABCE1's iron-sulfur cluster domain, which rotates 150 degrees into a binding pocket on the 40S subunit. This repositioning explains a newly observed anti-association activity of ABCE1. Notably, the movement implies a collision with A-site factors, thus explaining the splitting mechanism. Disruption of key interactions in the post-splitting complex impairs cellular homeostasis. Additionally, the structure of a native post-splitting complex reveals ABCE1 to be part of the 43S initiation complex, suggesting a coordination of termination, recycling, and initiation.