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EMD-2660 — Cryo-EM structure of the Plasmodium falciparum 80S ribosome bound to the anti-protozoan drug emetine — Wong W, Bai XC, Brown A, Fernandez IS, Hanssen E, Condron M, Tan YH, Baum J, Schere…
Cryo-EM structure of the small subunit of the mammalian mitochondrial ribosome.
Proc Natl Acad Sci U S A. 2014 May 20;111(20):7284-9
Authors: Kaushal PS, Sharma MR, Booth TM, Haque EM, Tung CS, Sanbonmatsu KY, Spremulli LL, Agrawal RK
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.
PMID: 24799711 [PubMed – indexed for MEDLINE]
The ribosome triggers the stringent response by RelA via a highly distorted tRNA.
EMBO Rep. 2013 Sep;14(9):811-6
Authors: Agirrezabala X, Fernández IS, Kelley AC, Cartón DG, Ramakrishnan V, Valle M
The bacterial stringent response links nutrient starvation with the transcriptional control of genes. This process is initiated by the stringent factor RelA, which senses the presence of deacylated tRNA in the ribosome as a symptom of amino-acid starvation to synthesize the alarmone (p)ppGpp. Here we report a cryo-EM study of RelA bound to ribosomes bearing cognate, deacylated tRNA in the A-site. The data show that RelA on the ribosome stabilizes an unusual distorted form of the tRNA, with the acceptor arm making contact with RelA and far from its normal location in the peptidyl transferase centre.
PMID: 23877429 [PubMed – indexed for MEDLINE]