title: Cryo-EM structure of the small subunit of the mammalian mitochondrial ribosome.
abstract: The mammalian mitochondrial ribosomes (mitoribosomes) are responsible for synthesizing 13 membrane proteins that form essential components of the complexes involved in oxidative phosphorylation or ATP generation for the eukaryotic cell. The mammalian 55S mitoribosome contains significantly smaller rRNAs and a large mass of mitochondrial ribosomal proteins (MRPs), including large mito-specific amino acid extensions and insertions in MRPs that are homologous to bacterial ribosomal proteins and an additional 35 mito-specific MRPs. Here we present the cryo-EM structure analysis of the small (28S) subunit (SSU) of the 55S mitoribosome. We find that the mito-specific extensions in homologous MRPs generally are involved in inter-MRP contacts and in contacts with mito-specific MRPs, suggesting a stepwise evolution of the current architecture of the mitoribosome. Although most of the mito-specific MRPs and extensions of homologous MRPs are situated on the peripheral regions, they also contribute significantly to the formation of linings of the mRNA and tRNA paths, suggesting a tailor-made structural organization of the mito-SSU for the recruitment of mito-specific mRNAs, most of which do not possess a 5' leader sequence. In addition, docking of previously published coordinates of the large (39S) subunit (LSU) into the cryo-EM map of the 55S mitoribosome reveals that mito-specific MRPs of both the SSU and LSU are involved directly in the formation of six of the 15 intersubunit bridges.
authors.affiliation: Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201;
authors.forename: Prem S
authors.initials: PS
authors.lastname: Kaushal
authors.affiliation: Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201;
authors.forename: Manjuli R
authors.initials: MR
authors.lastname: Sharma
authors.affiliation: Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201;
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Booth
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Emdadul M
authors.initials: EM
authors.lastname: Haque
authors.affiliation: Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545; and.
authors.forename: Chang-Shung
authors.initials: CS
authors.lastname: Tung
authors.affiliation: Theoretical Biology and Biophysics, Theoretical Division, Los Alamos National Laboratory, Los Alamos, NM 87545; and.
authors.forename: Karissa Y
authors.initials: KY
authors.lastname: Sanbonmatsu
authors.affiliation: Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599;
authors.forename: Linda L
authors.initials: LL
authors.lastname: Spremulli
authors.affiliation: Division of Translational Medicine, Wadsworth Center, New York State Department of Health, Albany, NY 12201;Department of Biomedical Sciences, School of Public Health, University at Albany, State University of New York, Albany, NY 12222 agrawal@wadsworth.org.
authors.forename: Rajendra K
authors.initials: RK
authors.lastname: Agrawal
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D020285:Cryoelectron Microscopy; D003593:Cytoplasm / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008099:Liver / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D011487:Protein Conformation; D012333:RNA, Messenger / Q000378:metabolism; D012336:RNA, Ribosomal, 16S / Q000378:metabolism; D012343:RNA, Transfer / Q000378:metabolism; D012269:Ribosomal Proteins / Q000378:metabolism; D012270:Ribosomes / Q000378:metabolism* / Q000648:ultrastructure*
chemical_list: D012333:RNA, Messenger; D012336:RNA, Ribosomal, 16S; D012269:Ribosomal Proteins; D012343:RNA, Transfer; D019204:GTP-Binding Proteins
keywords: cryo-electron microscopy; mammalian MRPs; mammalian mitochondrial ribosomal SSU; mito-12S rRNA