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vertebrate mitochondrial code

{{Short description|An alternative genetic code found in the mitochondrial genome of vertebrates}}

The vertebrate mitochondrial code (translation table 2) is the genetic code found in the mitochondria of all vertebrata.

Evolution

AGA and AGG were thought to have become mitochondrial stop codons early in vertebrate evolution. However, at least in humans it has now been shown that AGA and AGG sequences are not recognized as termination codons. A -1 mitoribosome frameshift occurs at the AGA and AGG codons predicted to terminate the CO1 and ND6 open reading frames (ORFs), and consequently both ORFs terminate in the standard UAG codon.

Incomplete stop codons

Mitochondrial genes in some vertebrates (including humans) have incomplete stop codons ending in U or UA, which become complete termination codons (UAA) upon subsequent polyadenylation.

Translation table

class="wikitable" style="border: none; text-align: center;"

| Amino acids biochemical properties

| style="background-color:#ffe75f; width: 50px;" | nonpolar

| style="background-color:#b3dec0; width: 50px;" | polar

| style="background-color:#bbbfe0; width: 50px;" | basic

| style="background-color:#f8b7d3; width: 50px;" | acidic

| style="border: none; width: 100px;" |

| style="background-color:#B0B0B0;" | Termination: stop codon

class="wikitable"

|+ Mitochondrial genetic code

!rowspan=2| 1st
base

!colspan=8| 2nd base

!rowspan=2| 3rd
base

colspan=2| U

!colspan=2| C

!colspan=2| A

!colspan=2| G

rowspan=4| U

| UUU

|rowspan=2 style="background-color:#ffe75f" | (Phe/F) Phenylalanine

| UCU

|rowspan=4 style="background-color:#b3dec0" | (Ser/S) Serine

| UAU

|rowspan=2 style="background-color:#b3dec0" | (Tyr/Y) Tyrosine

| UGU

|rowspan=2 style="background-color:#b3dec0" | (Cys/C) Cysteine

! U

UUC

| UCC

| UAC

| UGC

! C

UUA

|rowspan=6 style="background-color:#ffe75f" | (Leu/L) Leucine

| UCA

| UAA

|rowspan=2 style="background-color:#B0B0B0;" | Stop

| UGA

|rowspan=2 style="background-color:#ffe75f;" | (Trp/W) Tryptophan    

! A

UUG

| UCG

| UAG

| UGG

! G

rowspan="4" | C

| CUU

| CCU

|rowspan=4 style="background-color:#ffe75f" | (Pro/P) Proline

| CAU

|rowspan=2 style="background-color:#bbbfe0" | (His/H) Histidine

|CGU

|rowspan=4 style="background-color:#bbbfe0" | (Arg/R) Arginine

! U

CUC

|CCC

|CAC

|CGC

! C

CUA

|CCA

|CAA

|rowspan=2 style="background-color:#b3dec0" | (Gln/Q) Glutamine

|CGA

! A

CUG

|CCG

|CAG

|CGG

! G

rowspan="4" | A

|AUU

|rowspan=2 style="background-color:#ffe75f" | (Ile/I) Isoleucine

|ACU

|rowspan=4 style="background-color:#b3dec0" | (Thr/T) Threonine        

|AAU

|rowspan=2 style="background-color:#b3dec0" | (Asn/N) Asparagine

|AGU

|rowspan=2 style="background-color:#b3dec0" | (Ser/S) Serine

! U

AUC

|ACC

|AAC

|AGC

! C

AUA

|rowspan=2 style="background-color:#ffe75f" | (Met/M) Methionine

|ACA

|AAA

|rowspan=2 style="background-color:#bbbfe0" | (Lys/K) Lysine

|AGA

|rowspan=2 style="background-color:#B0B0B0;" | Stop

! A

AUG{{ref label|methionine|A|A}}

|ACG

|AAG

|AGG

! G

rowspan="4" | G

|GUU

|rowspan=4 style="background-color:#ffe75f" | (Val/V) Valine

|GCU

|rowspan=4 style="background-color:#ffe75f" | (Ala/A) Alanine

|GAU

|rowspan=2 style="background-color:#f8b7d3" | (Asp/D) Aspartic acid

|GGU

|rowspan=4 style="background-color:#ffe75f" | (Gly/G) Glycine

! U

GUC

|GCC

|GAC

|GGC

! C

GUA

|GCA

|GAA

|rowspan=2 style="background-color:#f8b7d3" | (Glu/E) Glutamic acid

|GGA

! A

GUG

|GCG

|GAG

|GGG

! G

:{{note label|methionine|A|A}} The codon AUG both codes for methionine and serves as an initiation site: the first AUG in an mRNA's coding region is where translation into protein begins.{{cite journal |author=Nakamoto T |title=Evolution and the universality of the mechanism of initiation of protein synthesis |journal=Gene |volume=432 |issue=1–2 |pages=1–6 | date=March 2009 |pmid=19056476 |doi=10.1016/j.gene.2008.11.001}}

Differences from the standard code

class="wikitable" style="border: none; text-align: center;"

|+

DNA codonsRNA codonsThis code (2)style="border: none; width: 1px;" |Standard code (1)
AGAAGAstyle="background-color:#B0B0B0;" | STOP = Ter (*)style="border: none; width: 1px;" |style="background-color:#bbbfe0;" | Arg (R)
AGGAGGstyle="background-color:#B0B0B0;" | STOP = Ter (*)style="border: none; width: 1px;" |style="background-color:#bbbfe0;" | Arg (R)
ATAAUAstyle="background-color:#ffe75f;" | Met (M)style="border: none; width: 1px;" |style="background-color:#ffe75f;" | Ile (I)
TGAUGAstyle="background-color:#ffe75f;" | Trp (W)style="border: none; width: 1px;" |style="background-color:#B0B0B0;" | STOP = Ter (*)

=Alternative initiation codons=

==See also==

References

  • This article contains public domain text from the NCBI page compiled by Andrzej Elzanowski and Jim Ostell.[https://www.ncbi.nlm.nih.gov/Taxonomy/taxonomyhome.html/index.cgi?chapter=tgencodes#thetop The Genetic Codes]

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{{Use dmy dates|date=October 2019}}

Category:Molecular genetics

Category:Gene expression

Category:Protein biosynthesis