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Elife. 2018 Nov 26;7. pii: e39163. doi: 10.7554/eLife.39163.

The CryoEM structure of the Saccharomyces cerevisiae ribosome maturation factor Rea1.

Sosnowski P#1,2,3,4, Urnavicius L#5, Boland A5, Fagiewicz R1,2,3,4, Busselez J1,2,3,4, Papai G1,2,3,4, Schmidt H1,2,3,4.

Author information

1
Institut de Génétique et de Biologie Moléculaire et Cellulaire, Illkirch, France.
2
Centre National de la Recherche Scientifique, UMR7104, Illkirch, France.
3
Institut National de la Santé et de la Recherche Médicale, U964, Illkirch, France.
4
Université de Strasbourg, Illkirch, France.
5
Division of Structural Studies, MRC Laboratory of Molecular Biology, Cambridge, United Kingdom.
#
Contributed equally

Abstract

The biogenesis of 60S ribosomal subunits is initiated in the nucleus where rRNAs and proteins form pre-60S particles. These pre-60S particles mature by transiently interacting with various assembly factors. The ~5000 amino-acid AAA+ ATPase Rea1 (or Midasin) generates force to mechanically remove assembly factors from pre-60S particles, which promotes their export to the cytosol. Here we present three Rea1 cryoEM structures. We visualise the Rea1 engine, a hexameric ring of AAA+ domains, and identify an α-helical bundle of AAA2 as a major ATPase activity regulator. The α-helical bundle interferes with nucleotide-induced conformational changes that create a docking site for the substrate binding MIDAS domain on the AAA +ring. Furthermore, we reveal the architecture of the Rea1 linker, which is involved in force generation and extends from the AAA+ ring. The data presented here provide insights into the mechanism of one of the most complex ribosome maturation factors.

KEYWORDS:

AAA+ protein; CryoEM; Rea1; S. cerevisiae; midasin; molecular biophysics; molecular machine; ribosome maturation; structural biology

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