1. Cryo-EM reveals active site coordination within a multienzyme pre-rRNA processing complex
- Author
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Monica C. Pillon, Mack Sobhany, Mario J. Borgnia, Juno M. Krahn, Allen L. Hsu, Jason Williams, Robin E. Stanley, and Kevin H Goslen
- Subjects
Protein Conformation ,RNase P ,Endoribonuclease ,02 engineering and technology ,Chaetomium ,010403 inorganic & nuclear chemistry ,01 natural sciences ,Biochemistry ,Ribosome ,Article ,Ribosome assembly ,Fungal Proteins ,Inorganic Chemistry ,03 medical and health sciences ,0302 clinical medicine ,Multienzyme Complexes ,Structural Biology ,Catalytic Domain ,RNA Precursors ,General Materials Science ,Physical and Theoretical Chemistry ,RRNA processing ,Molecular Biology ,030304 developmental biology ,0303 health sciences ,Nuclease ,biology ,Chemistry ,Cryoelectron Microscopy ,RNA ,Ribosomal RNA ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,0104 chemical sciences ,biology.protein ,0210 nano-technology ,030217 neurology & neurosurgery - Abstract
Ribosome assembly is a complex process reliant on the coordination of trans-acting enzymes to produce functional ribosomal subunits and secure the translational capacity of cells. The endoribonuclease (RNase) Las1 and the poly-nucleotide kinase (PNK) Grc3 assemble into a multienzyme complex, herein designated RNase PNK, to orchestrate processing of precursor ribosomal RNA. RNase PNK belongs to the functionally-diverse HEPN nuclease superfamily, whose members rely on distinct cues for nuclease activation. To establish how RNase PNK coordinates its dual enzymatic activities, we solved a series of cryo-electron microscopy structures of Chaetomium thermophilum RNase PNK in multiple conformational states. The structures reveal that RNase PNK adopts a butterfly-like architecture harboring a composite HEPN nuclease active site flanked by discrete RNA kinase sites. We identify two molecular switches that coordinate nuclease and kinase function. Together our structures and corresponding functional studies establish a new mechanism of HEPN nuclease activation essential for ribosome production.
- Published
- 2019