The mitochondrial ribosome, or mitoribosome, is a ribonucleoprotein complex that is active in mitochondria and functions as a riboprotein for translating mitochondrial encoded in mtDNA. The mitoribosome is attached to the inner mitochondrial membrane.
Function
Mitochondria need around 1000 different proteins in
yeast and 1500 different proteins in
Human to work. However, only 8 and 13 proteins are encoded in mitochondrial DNA in yeast and humans, respectively. So most mitochondrial proteins are encoded in the nucleus and are synthesized by cytoplasmic ribosomes.
Some of the proteins that are key components in the electron transport chain are encoded and translated within mitochondria.
Structure
Mammals mitoribosomes have small 28S and large 39S subunits, together forming a 55S mitoribosome.
Plant mitoribosomes have small 33S and large 50S subunits, together forming a 78S mitoribosome.
Animal mitoribosomes only have two rRNAs, 12S (SSU) and 16S (LSU), both highly minimized compared to their larger bacterial homologues.
Comparison to other ribosomes
Like mitochondria itself is descended from bacteria, mitochondrial ribosomes are descended from bacterial ribosomes.
As mitochondria evolved however, the mitoribosome has significantly diverged from its bacterial cousins leading to differences in configuration and function.
In configuration, the mitoribosome includes additional proteins in both its large and small subunits.
In function, mitoribosomes are much more limited in the proteins they translate, only producing a few proteins, used mostly in the mitochondrial membrane.
Below is a table showing some properties of different ribosomes:
+Properties of mitoribosomes
!
!Bacteria |
|
|
|
Diseases
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.
In humans, disease particularly manifests in energy-reliant organs such as the
heart,
brain, and
Skeletal muscle.
Disease either originates from
Mutation in mitochondrial rRNA or
Gene encoding the mitoribosomal proteins.
In the case of mitoribosomal protein mutation,
heredity of disease follows Mendelian inheritance as these proteins are encoded in the nucleus.
On the other hand, because mitochondrial rRNA is encoded in the mitochondria, mutations in rRNA are maternally inherited.
Examples of diseases in humans caused by these mutations include
Leigh syndrome, deafness, neurological disorders, and various
Cardiomyopathy.
In
Plant, mutation in mitoribosomal proteins can result in stunted size and distorted leaf growth.
Genes
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 .)
-
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)
Further reading
