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- Itoh, Yuzuru, et al.
(författare)
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Mechanism of membrane-tethered mitochondrial protein synthesis
- 2021
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 371:6531, s. 846-849
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Tidskriftsartikel (refereegranskat)abstract
- Mitochondrial ribosomes (mitoribosomes) are tethered to the mitochondrial inner membrane to facilitate the cotranslational membrane insertion of the synthesized proteins. We report cryo-electron microscopy structures of human mitoribosomes with nascent polypeptide, bound to the insertase oxidase assembly 1-like (OXA1L) through three distinct contact sites. OXA1L binding is correlated with a series of conformational changes in the mitoribosomal large subunit that catalyze the delivery of newly synthesized polypeptides. The mechanism relies on the folding of mL45 inside the exit tunnel, forming two specific constriction sites that would limit helix formation of the nascent chain. A gap is formed between the exit and the membrane, making the newly synthesized proteins accessible. Our data elucidate the basis by which mitoribosomes interact with the OXA1L insertase to couple protein synthesis and membrane delivery.
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| 2. |
- Singh, Vivek, et al.
(författare)
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Structural basis of LRPPRC-SLIRP-dependent translation by the mitoribosome
- 2022
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- In mammalian mitochondria, mRNAs are co-transcriptionally stabilized by the protein factor LRPPRC. Here, we characterize LRPPRC as an mRNA delivery factor and report its cryo-EM structure in complex with SLIRP, mRNA and the mitoribosome. The structure shows that LRPPRC associates with the mitoribosomal proteins mS39 and the N-terminus of mS31 through recognition of eight of the LRPPRC helical repeats. Together, the proteins form a corridor for hand-off the mRNA. The mRNA is directly bound to SLIRP, which also has a stabilizing function for LRPPRC. To delineate the effect of LRPPRC on individual mitochondrial transcripts, we used an RNAseq approach, metabolic labeling and mitoribosome profiling that showed a major influence onND1, ND2, ATP6, COX1, COX2,andCOX3mRNA translation efficiency. Taken together, our data suggest that LRPPRC-SLIRP does not preexist on the mitoribosome as its structural element but rather acts in recruitment of specific mRNAs to modulate their translation. Collectively, the data define LRPPRC-SLIRP as a regulator of the mitochondrial gene expression system.
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