Nmd3 is a structural mimic of eIF5A, and activates the cpGTPase Lsg1 during 60S ribosome biogenesis.
During ribosome biogenesis in eukaryotes, nascent subunits are exported to the cytoplasm in a functionally inactive state. 60S subunits are activated through a series of cytoplasmic maturation events. The last known events in the cytoplasm are the release of Tif6 by Efl1 and Sdo1 and the release of the export adapter, Nmd3, by the GTPase Lsg1. Here, we have used cryo-electron microscopy to determine the structure of the 60S subunit bound by Nmd3, Lsg1, and Tif6. We find that a central domain of Nmd3 mimics the translation elongation factor eIF5A, inserting into the E site of the ribosome and pulling the L1 stalk into a closed position. Additional domains occupy the P site and extend toward the sarcin-ricin loop to interact with Tif6. Nmd3 and Lsg1 together embrace helix 69 of the B2a intersubunit bridge, inducing base flipping that we suggest may activate the GTPase activity of Lsg1.
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA.
Andrey G
AG
Malyutin
Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, USA.
Sharmishtha
S
Musalgaonkar
Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, USA.
Stephanie
S
Patchett
Department of Biochemistry and Molecular Biophysics, Columbia University, New York, NY, USA jf2192@cumc.columbia.edu arlen@mail.utexas.edu.|Department of Biological Sciences, Columbia University, New York, NY, USA.|Howard Hughes Medical Institute, Columbia University, New York, NY, USA.
Joachim
0000-0001-5449-6943
J
Frank
Department of Molecular Biosciences, The University of Texas at Austin, Austin, TX, USA jf2192@cumc.columbia.edu arlen@mail.utexas.edu.
Arlen W
0000-0002-4742-085X
AW
Johnson
D020285:Cryoelectron Microscopy; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D001678:Organelle Biogenesis; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D012269:Ribosomal Proteins / Q000737:chemistry / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000378:metabolism* / Q000648:ultrastructure; D012441:Saccharomyces cerevisiae / Q000737:chemistry / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000378:metabolism*
C117894:NMD3 protein, S cerevisiae; D016601:RNA-Binding Proteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; C491609:TIF6 protein, S cerevisiae; D019204:GTP-Binding Proteins; C475026:LSG1 protein, S cerevisiae
LSG1; NMD3; eIF5A; ribosome biogenesis