title: Cryo-EM structure of the spinach chloroplast ribosome reveals the location of plastid-specific ribosomal proteins and extensions.
abstract: Ribosomes are the protein synthesizing machines of the cell. Recent advances in cryo-EM have led to the determination of structures from a variety of species, including bacterial 70S and eukaryotic 80S ribosomes as well as mitoribosomes from eukaryotic mitochondria, however, to date high resolution structures of plastid 70S ribosomes have been lacking. Here we present a cryo-EM structure of the spinach chloroplast 70S ribosome, with an average resolution of 5.4 Å for the small 30S subunit and 3.6 Å for the large 50S ribosomal subunit. The structure reveals the location of the plastid-specific ribosomal proteins (RPs) PSRP1, PSRP4, PSRP5 and PSRP6 as well as the numerous plastid-specific extensions of the RPs. We discover many features by which the plastid-specific extensions stabilize the ribosome via establishing additional interactions with surrounding ribosomal RNA and RPs. Moreover, we identify a large conglomerate of plastid-specific protein mass adjacent to the tunnel exit site that could facilitate interaction of the chloroplast ribosome with the thylakoid membrane and the protein-targeting machinery. Comparing the Escherichia coli 70S ribosome with that of the spinach chloroplast ribosome provides detailed insight into the co-evolution of RP and rRNA.
authors.affiliation: Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Graf
authors.affiliation: Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Arenz
authors.affiliation: Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany.
authors.forename: Paul
authors.initials: P
authors.lastname: Huter
authors.affiliation: Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Dönhöfer
authors.affiliation: Central European Institute of Technology (CEITEC), Masaryk University, Kamenice 5, 62500 Brno, Czech Republic.
authors.forename: Jirí
authors.initials: J
authors.lastname: Novácek
authors.affiliation: Gene Center, Department for Biochemistry and Center for integrated Protein Science Munich (CiPSM), University of Munich, 81377 Munich, Germany.|Department of Biochemistry and Molecular Biology, University of Hamburg, 20146 Hamburg, Germany.
authors.forename: Daniel N
authors.initials: DN
authors.lastname: Wilson
mesh_terms: D001665:Binding Sites; D060365:Chloroplast Proteins / Q000737:chemistry* / Q000378:metabolism; D002736:Chloroplasts / Q000737:chemistry*; D020285:Cryoelectron Microscopy; D008958:Models, Molecular; D020871:RNA Stability; D012335:RNA, Ribosomal / Q000737:chemistry; D012269:Ribosomal Proteins / Q000737:chemistry* / Q000378:metabolism; D054683:Ribosome Subunits, Large, Eukaryotic / Q000737:chemistry* / Q000378:metabolism; D054682:Ribosome Subunits, Small, Eukaryotic / Q000737:chemistry*; D018724:Spinacia oleracea / Q000737:chemistry*
chemical_list: D060365:Chloroplast Proteins; D012335:RNA, Ribosomal; D012269:Ribosomal Proteins