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Revised intro adding that proteins are assembled in cytoplasm first, added Disease section with some human and plant diseases. Removed "missing non-animal info" tag.
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[[File:Mitochondrion structure.svg|thumb|300px|A diagram showing [[mtDNA]] (circular) and mitochondrial ribosomes among other mitochondria structures]] |
[[File:Mitochondrion structure.svg|thumb|300px|A diagram showing [[mtDNA]] (circular) and mitochondrial ribosomes among other mitochondria structures]] |
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The '''mitochondrial ribosome''', or '''mitoribosome''', is a [[Protein complexes|protein complex]] that is active in [[mitochondria]] and functions as a [[Ribosomal protein|riboprotein]] for [[Translation (biology)|translating]] mitochondrial [[mRNA]]s encoded in [[mtDNA]]. The mitoribosome is attached to the [[inner mitochondrial membrane]].<ref name=":02" /> Mitoribosomes, like [[cytoplasm]]ic [[ribosome]]s, consist of two subunits — large (mtLSU) and small (mt-SSU).<ref name="AmuntsBrown2015">{{cite journal | vauthors = Amunts A, Brown A, Toots J, Scheres SH, Ramakrishnan V | title = Ribosome. The structure of the human mitochondrial ribosome | journal = Science | volume = 348 | issue = 6230 | pages = 95–98 | date = April 2015 | pmid = 25838379 | pmc = 4501431 | doi = 10.1126/science.aaa1193 }}</ref> Mitoribosomes consist of several specific proteins and fewer rRNAs.<ref name="AmuntsBrown2015"/> While mitochondrial rRNAs are encoded in the [[Mitochondrial DNA|mitochondrial genome]], the proteins that make up mitoribosomes are encoded in the nucleus and assembled by cytoplasmic ribosomes before being implanted into the mitochondria.<ref name=":3">{{ |
The '''mitochondrial ribosome''', or '''mitoribosome''', is a [[Protein complexes|protein complex]] that is active in [[mitochondria]] and functions as a [[Ribosomal protein|riboprotein]] for [[Translation (biology)|translating]] mitochondrial [[mRNA]]s encoded in [[mtDNA]]. The mitoribosome is attached to the [[inner mitochondrial membrane]].<ref name=":02" /> Mitoribosomes, like [[cytoplasm]]ic [[ribosome]]s, consist of two subunits — large (mtLSU) and small (mt-SSU).<ref name="AmuntsBrown2015">{{cite journal | vauthors = Amunts A, Brown A, Toots J, Scheres SH, Ramakrishnan V | title = Ribosome. The structure of the human mitochondrial ribosome | journal = Science | volume = 348 | issue = 6230 | pages = 95–98 | date = April 2015 | pmid = 25838379 | pmc = 4501431 | doi = 10.1126/science.aaa1193 }}</ref> Mitoribosomes consist of several specific proteins and fewer rRNAs.<ref name="AmuntsBrown2015"/> While mitochondrial rRNAs are encoded in the [[Mitochondrial DNA|mitochondrial genome]], the proteins that make up mitoribosomes are encoded in the nucleus and assembled by cytoplasmic ribosomes before being implanted into the mitochondria.<ref name=":3">{{cite journal | vauthors = Sylvester JE, Fischel-Ghodsian N, Mougey EB, O'Brien TW | title = Mitochondrial ribosomal proteins: candidate genes for mitochondrial disease | journal = Genetics in Medicine | volume = 6 | issue = 2 | pages = 73–80 | date = March 2003 | pmid = 15017329 | doi = 10.1097/01.GIM.0000117333.21213.17 }}</ref> |
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== Function == |
== Function == |
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== Diseases == |
== Diseases == |
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As the mitoribosome is responsible for the manufacture of proteins necessary for the [[electron transport chain]], malfunctions in the mitoribosome can result in metabolic disease.<ref name=":12">{{ |
As the mitoribosome is responsible for the manufacture of proteins necessary for the [[electron transport chain]], malfunctions in the mitoribosome can result in metabolic disease.<ref name=":12">{{cite journal | vauthors = De Silva D, Tu YT, Amunts A, Fontanesi F, BarrientosA| title = Mitochondrial ribosome assembly in health and disease | journal = Cell Cycle | volume = 14 | issue = 14 | pages = 2226–2250 | date = 2015-07-18 | pmid = 26030272 | pmc = 4615001 | doi = 10.1080/15384101.2015.1053672 }}</ref> <ref name=":3" /> In humans, disease particularly manifests in energy-reliant organs such as the heart, brain, and muscle.<ref name=":3" /> Disease either originates from mutations in mitochondrial rRNA or genes encoding the mitoribosomal proteins.<ref name=":3" /> In the case of mitoribosomal protein mutation, heredity of disease follows [[Mendelian inheritance]] as these proteins are encoded in the nucleus.<ref name=":12" /> On the other hand, because mitochondrial rRNA is encoded in the mitochondria, mutations in rRNA are maternally inherited.<ref name=":12" /> Examples of diseases in humans caused by these mutations include [[Leigh syndrome]], deafness, neurological disorders, and various cardiomyopathies.<ref name=":12" /> In plants, mutation in mitoribosomal proteins can result in stunted size and distorted leaf growth.<ref name=":2">{{cite journal | vauthors = Robles P, Quesada V| title = Emerging Roles of Mitochondrial Ribosomal Proteins in Plant Development | journal = International Journal of Molecular Sciences | volume = 18 | issue = 12 | date = December 2017 | pmid = 29207474 | pmc = 5751198 | doi = 10.3390/ijms18122595 }}</ref> |
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== Genes == |
== Genes == |
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The mitochondrial ribosome, or mitoribosome, is a protein complex that is active in mitochondria and functions as a riboprotein for translating mitochondrial mRNAs encoded in mtDNA. The mitoribosome is attached to the inner mitochondrial membrane.[1] Mitoribosomes, like cytoplasmic ribosomes, consist of two subunits — large (mtLSU) and small (mt-SSU).[2] Mitoribosomes consist of several specific proteins and fewer rRNAs.[2] While mitochondrial rRNAs are encoded in the mitochondrial genome, the proteins that make up mitoribosomes are encoded in the nucleus and assembled by cytoplasmic ribosomes before being implanted into the mitochondria.[3]
Mitochondria contain around 1000 proteins in yeast and 1500 proteins in humans. However, only 8 and 13 proteins are encoded in mitochondrial DNA in yeast and humans respectively. Most mitochondrial proteins are synthesized via cytoplasmic ribosomes.[4] Proteins that are key components in the electron transport chain are translated in mitochondria.[5][6]
Mammalian mitoribosomes 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]
Animal mitoribosomes only have two rRNAs, 12S (SSU) and 16S (LSU), both highly minimized compared to their larger homologues.[7] Most eukaryotoes use 5S mitoribosomal RNA, animals, fungi, alveolates and euglenozoans being 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]
Like the mitochondria itself, mitochondrial ribosomes are descended from bacterial ribosomes. [1] However, there has been significant divergence between the two as mitochondria evolved, 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) |
As the mitoribosome is responsible for the manufacture of proteins necessary for the electron transport chain, malfunctions in the mitoribosome can result in metabolic disease.[13] [3] In humans, disease particularly manifests in energy-reliant organs such as the heart, brain, and muscle.[3] Disease either originates from mutations in mitochondrial rRNA or genes encoding the mitoribosomal proteins.[3] In the case of mitoribosomal protein mutation, heredity of disease follows Mendelian inheritance as 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 include Leigh syndrome, deafness, neurological disorders, and various cardiomyopathies.[13] In plants, mutation in mitoribosomal proteins can result in stunted size and distorted leaf growth.[14]
The mitochondrial ribosomal protein nomenclature generally follows that of bacteria, with extra numbers used for mitochondrion-specific proteins. (For more information on the nomenclature, see Ribosomal protein § Table of ribosomal proteins.)
{{cite journal}}: CS1 maint: unflagged free DOI (link)
{{cite journal}}: CS1 maint: unflagged free DOI (link)
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Ribosomal RNA / ribosome subunits
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| Archaea (70S) |
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| Ribosomal proteins | (See article table) | ||||||
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