Themitochondrial ribosome,ormitoribosome,is aprotein complexthat is active inmitochondriaand functions as ariboproteinfortranslatingmitochondrialmRNAsencoded inmtDNA.The mitoribosome is attached to theinner mitochondrial membrane.[1]Mitoribosomes, likecytoplasmicribosomes,consist of two subunits — large (mt-LSU) and small (mt-SSU).[2]Mitoribosomes consist of several specific proteins and fewer rRNAs.[2]While mitochondrial rRNAs are encoded in themitochondrial genome,the proteins that make up mitoribosomes are encoded in thenucleusand assembled by cytoplasmic ribosomes before being implanted into the mitochondria.[3]
Function
editMitochondria contain around 1000 proteins inyeastand 1500 proteins inhumans.However, only 8 and 13 proteins are encoded inmitochondrial DNAin yeast and humans respectively. Most mitochondrial proteins are synthesized via cytoplasmic ribosomes.[4]Proteins that are key components in theelectron transport chainare translated in mitochondria.[5][6]
Structure
editMammalianmitoribosomes have small 28S and large 39S subunits, together forming a 55S mitoribosome.[7][8]Plant mitoribosomes have small 33S and large 50S subunits, together forming a 78S mitoribosome.[7][8]
Animalmitoribosomes only have two rRNAs, 12S (SSU) and 16S (LSU), both highly minimized compared to their larger homologues.[7]Most eukaryotoes use5S mitoribosomal RNA,animals,fungi,alveolatesandeuglenozoansbeing the exceptions.[9]A variety of methods have evolved to fill in the gap left by a missing 5S, with animals co-opting a Mt-tRNA (Val in vertebrates).[7][10]
Comparison to other ribosomes
editLike mitochondria itself is descended from bacteria, mitochondrial ribosomes are descended from bacterial ribosomes.[1]As mitochondria evolved however, the mitoribosome has significantly diverged from its bacterial cousins leading to differences in configuration and function.[1]In configuration, the mitoribosome includes additional proteins in both its large and small subunits.[1]In function, mitoribosomes are much more limited in the proteins they translate, only producing a few proteins, used mostly in the mitochondrial membrane.[1]Below is a table showing some properties of different ribosomes:
| Bacteria[1][11] | Cytosolic (Eukaryote)[11][1] | Mammalian mitochondria[1][11] | Yeast Mitochondria[1][11] | Plant Mitochondria[12] | |
|---|---|---|---|---|---|
| Sedimentation Coefficient(LSU/SSU) | 70S (50S/30S) | 80S (60S/40S) | 55S (39S/28S) | 74S (54S/37S) | ~80S |
| Number of proteins (LSU/SSU) | 54 (33/21) | 79-80 (46-47/33) | 80 (50/30) | 84 (46/38) | 68-80 |
| Number of rRNAs (LSU/SSU) | 3 (2/1) | 4 (3/1) | 3 (2/1) | 2 (1/1) | 3 (2/1) |
Diseases
editAs the mitoribosome is responsible for the manufacture of proteins necessary for theelectron transport chain,malfunctions in the mitoribosome can result in metabolic disease.[13][3]In humans, disease particularly manifests in energy-reliant organs such as theheart,brain,andmuscle.[3]Disease either originates frommutationsin mitochondrial rRNA orgenesencoding the mitoribosomal proteins.[3]In the case of mitoribosomal protein mutation,heredityof disease followsMendelian inheritanceas these proteins are encoded in the nucleus.[13]On the other hand, because mitochondrial rRNA is encoded in the mitochondria, mutations in rRNA are maternally inherited.[13]Examples of diseases in humans caused by these mutations includeLeigh syndrome,deafness,neurological disorders,and variouscardiomyopathies.[13]Inplants,mutation in mitoribosomal proteins can result in stunted size and distorted leaf growth.[14]
Genes
editThe mitochondrial ribosomal protein nomenclature generally follows that of bacteria, with extra numbers used for mitochondrion-specific proteins. (For more information on the nomenclature, seeRibosomal protein § Table of ribosomal proteins.)
- MRPS1,MRPS2,MRPS3,MRPS4,MRPS5,MRPS6,MRPS7,MRPS8,MRPS9,MRPS10,MRPS11,MRPS12,MRPS13,MRPS14,MRPS15,MRPS16,MRPS17,MRPS18,MRPS19,MRPS20,MRPS21,MRPS22,MRPS23,MRPS24,MRPS25,MRPS26,MRPS27,MRPS28,MRPS29,MRPS30,MRPS31,MRPS32,MRPS33,MRPS34,MRPS35
- MRPL1,MRPL2,MRPL3,MRPL4,MRPL5,MRPL6,MRPL7,MRPL8,MRPL9,MRPL10,MRPL11,MRPL12,MRPL13,MRPL14,MRPL15,MRPL16,MRPL17,MRPL18,MRPL19,MRPL20,MRPL21,MRPL22,MRPL23,MRPL24,MRPL25,MRPL26,MRPL27,MRPL28,MRPL29,MRPL30,MRPL31,MRPL32,MRPL33,MRPL34,MRPL35,MRPL36,MRPL37,MRPL38,MRPL39,MRPL40,MRPL41,MRPL42
- rRNA:MT-RNR1,MT-RNR2,MT-TV (mitochondrial)
References
edit- ^abcdefghiGreber BJ, Ban N (June 2016)."Structure and Function of the Mitochondrial Ribosome".Annual Review of Biochemistry.85(1): 103–132.doi:10.1146/annurev-biochem-060815-014343.PMID27023846.
- ^abAmunts A, Brown A, Toots J, Scheres SH, Ramakrishnan V (April 2015)."Ribosome. The structure of the human mitochondrial ribosome".Science.348(6230): 95–98.doi:10.1126/science.aaa1193.PMC4501431.PMID25838379.
- ^abcdSylvester JE, Fischel-Ghodsian N, Mougey EB, O'Brien TW (March 2003)."Mitochondrial ribosomal proteins: candidate genes for mitochondrial disease".Genetics in Medicine.6(2): 73–80.doi:10.1097/01.GIM.0000117333.21213.17.PMID15017329.S2CID22169585.
- ^Wenz LS, Opaliński Ł, Wiedemann N, Becker T (May 2015)."Cooperation of protein machineries in mitochondrial protein sorting".Biochimica et Biophysica Acta (BBA) - Molecular Cell Research.1853(5): 1119–1129.doi:10.1016/j.bbamcr.2015.01.012.PMID25633533.
- ^Johnston IG, Williams BP (February 2016)."Evolutionary Inference across Eukaryotes Identifies Specific Pressures Favoring Mitochondrial Gene Retention".Cell Systems.2(2): 101–111.doi:10.1016/j.cels.2016.01.013.PMID27135164.
- ^Hamers L (2016). "Why do our cell's power plants have their own DNA?".Science.doi:10.1126/science.aaf4083.
- ^abcdGreber BJ, Bieri P, Leibundgut M, Leitner A, Aebersold R, Boehringer D, Ban N (April 2015). "Ribosome. The complete structure of the 55S mammalian mitochondrial ribosome".Science.348(6232): 303–308.doi:10.1126/science.aaa3872.hdl:20.500.11850/100390.PMID25837512.S2CID206634178.
- ^abSpremulli LL (2016-01-01). "The Protein Biosynthetic Machinery of Mitochondria". In Bradshaw RA, Stahl PD (eds.).Encyclopedia of Cell Biology.Waltham: Academic Press. pp. 545–554.doi:10.1016/b978-0-12-394447-4.10066-5.ISBN978-0-12-394796-3.
- ^Valach M, Burger G, Gray MW, Lang BF (December 2014)."Widespread occurrence of organelle genome-encoded 5S rRNAs including permuted molecules".Nucleic Acids Research.42(22): 13764–13777.doi:10.1093/nar/gku1266.PMC4267664.PMID25429974.
- ^Brown A, Amunts A, Bai XC, Sugimoto Y, Edwards PC, Murshudov G, et al. (November 2014)."Structure of the large ribosomal subunit from human mitochondria".Science.346(6210): 718–722.Bibcode:2014Sci...346..718B.doi:10.1126/science.1258026.PMC4246062.PMID25278503.
- ^abcdDe Silva D, Tu YT, Amunts A, Fontanesi F, Barrientos A (2015-07-18)."Mitochondrial ribosome assembly in health and disease".Cell Cycle.14(14): 2226–2250.doi:10.1080/15384101.2015.1053672.PMC4615001.PMID26030272.
- ^Robles P, Quesada V (December 2017)."Emerging Roles of Mitochondrial Ribosomal Proteins in Plant Development".International Journal of Molecular Sciences.18(12): 2595.doi:10.3390/ijms18122595.PMC5751198.PMID29207474.
- ^abcdDe Silva D, Tu YT, Amunts A, Fontanesi F, Barrientos A (2015-07-18)."Mitochondrial ribosome assembly in health and disease".Cell Cycle.14(14): 2226–2250.doi:10.1080/15384101.2015.1053672.PMC4615001.PMID26030272.
- ^Robles P, Quesada V (December 2017)."Emerging Roles of Mitochondrial Ribosomal Proteins in Plant Development".International Journal of Molecular Sciences.18(12): 2595.doi:10.3390/ijms18122595.PMC5751198.PMID29207474.
Further reading
edit- Greber BJ, Ban N (June 2016)."Structure and Function of the Mitochondrial Ribosome".Annual Review of Biochemistry.85:103–132.doi:10.1146/annurev-biochem-060815-014343.PMID27023846.