PSRP1 is not a ribosomal protein, but a ribosome-binding factor that is recycled by the ribosome-recycling factor (RRF) and elongation factor G (EF-G).
Plastid-specific ribosomal proteins (PSRPs) have been proposed to play roles in the light-dependent regulation of chloroplast translation. Here we demonstrate that PSRP1 is not a bona fide ribosomal protein, but rather a functional homologue of the Escherichia coli cold-shock protein pY. Three-dimensional Cryo-electron microscopic (Cryo-EM) reconstructions reveal that, like pY, PSRP1 binds within the intersubunit space of the 70S ribosome, at a site overlapping the positions of mRNA and A- and P-site tRNAs. PSRP1 induces conformational changes within ribosomal components that comprise several intersubunit bridges, including bridge B2a, thereby stabilizes the ribosome against dissociation. We find that the presence of PSRP1/pY lowers the binding of tRNA to the ribosome. Furthermore, similarly to tRNAs, PSRP1/pY is recycled from the ribosome by the concerted action of the ribosome-recycling factor (RRF) and elongation factor G (EF-G). These results suggest a novel function for EF-G and RRF in the post-stress return of PSRP1/pY-inactivated ribosomes to the actively translating pool.
Sharma
Manjuli R
MR
From the Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, New York 12201-0509.
Dönhöfer
Alexandra
A
the Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universitat München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany; Gene Center and Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universitat München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany.
Barat
Chandana
C
From the Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, New York 12201-0509.
Marquez
Viter
V
the Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universitat München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany; Gene Center and Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universitat München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany.
Datta
Partha P
PP
From the Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, New York 12201-0509.
Fucini
Paola
P
the Cluster of Excellence for Macromolecular Complexes, Institut fur Organische Chemie und Chemische Biologie, J. W. Goethe-Universitaet Frankfurt am Main, Max-von-Laue-Strasse 7, D-60438 Frankfurt am Main, Germany, and.
Wilson
Daniel N
DN
the Center for Integrated Protein Science Munich (CiPSM), Ludwig-Maximilians-Universitat München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany; Gene Center and Department of Chemistry and Biochemistry, Ludwig-Maximilians-Universitat München, Feodor-Lynen-Strasse 25, D-81377 Munich, Germany. Electronic address: wilson@lmb.uni-muenchen.de.
Agrawal
Rajendra K
RK
From the Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Empire State Plaza, Albany, New York 12201-0509; the Department of Biomedical Sciences, School of Public Health, State University of New York at Albany, Albany, New York 12201. Electronic address: agrawal@wadsworth.org.
D000595:Amino Acid Sequence; D001665:Binding Sites / Q000235:genetics; D002352:Carrier Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D020285:Cryoelectron Microscopy; D018360:Crystallography, X-Ray; D004591:Electrophoresis, Polyacrylamide Gel; D004926:Escherichia coli / Q000378:metabolism; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D018087:Plastids / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012269:Ribosomal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D054657:Ribosome Subunits / Q000737:chemistry / Q000378:metabolism / Q000648:ultrastructure; D012270:Ribosomes / Q000737:chemistry / Q000378:metabolism* / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D018724:Spinacia oleracea / Q000235:genetics / Q000378:metabolism
D002352:Carrier Proteins; D010940:Plant Proteins; D012269:Ribosomal Proteins