Invertebrate mitochondrial code

Short description: An alternative genetic code found in the mitochondrial genome of some invertebrates

The invertebrate mitochondrial code (translation table 5) is a genetic code used by the mitochondrial genome of invertebrates. Mitochondria contain their own DNA and reproduce independently from their host cell. Variation in translation of the mitochondrial genetic code occurs when DNA codons result in non-standard amino acids has been identified in invertebrates, most notably arthropods.[1] This variation has been helpful as a tool to improve upon the phylogenetic tree of invertebrates, like flatworms.[2]

## Contents

* 1 The code
* 2 Differences from the standard code
* 2.1 Alternative initiation codons
* 3 Systematic range
* 4 Other variations
* 5 See also
* 6 References

## The code

` AAs = FFLLSSSSYY**CCWWLLLLPPPPHHQQRRRRIIMMTTTTNNKKSSSSVVVVAAAADDEEGGGG`
`Starts = 
M

-MMMM

M

`
` Base1 = TTTTTTTTTTTTTTTTCCCCCCCCCCCCCCCCAAAAAAAAAAAAAAAAGGGGGGGGGGGGGGGG`
` Base2 = TTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGGTTTTCCCCAAAAGGGG`
` Base3 = TCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAGTCAG`

Bases: adenine (A), cytosine (C), guanine (G) and thymine (T) or uracil (U).

Amino acids: Alanine (Ala, A), Arginine (Arg, R), Asparagine (Asn, N), Aspartic acid (Asp, D), Cysteine (Cys, C), Glutamic acid (Glu, E), Glutamine (Gln, Q), Glycine (Gly, G), Histidine (His, H), Isoleucine (Ile, I), Leucine (Leu, L), Lysine (Lys, K), Methionine (Met, M), Phenylalanine (Phe, F), Proline (Pro, P), Serine (Ser, S), Threonine (Thr, T), Tryptophan (Trp, W), Tyrosine (Tyr, Y), Valine (Val, V).

## Differences from the standard code

DNA codons | RNA codons | This code (5) |  | Standard code (1)

|
|
|
|

AGA | AGA | Ser (S) |  | Arg (R)
AGG | AGG | Ser (S) |  | Arg (R)
ATA | AUA | Met (M) |  | Ile (I)
TGA | UGA | Trp (W) |  | STOP = Ter (*)

Note: The codon AGG is absent in Drosophila.[3]

### Alternative initiation codons

* ATA/AUA
* ATT/AUU
* ATC/AUC: Apis[4]
* GTG/GUG: Polyplacophora[5]
* TTG/UUG: Ascaris, Caenorhabditis.

## Systematic range

* Nematoda: Ascaris, Caenorhabditis ;
* Mollusca: Bivalvia);[6] Polyplacophora;[5]
* Arthropoda/Crustacea: Artemia;[7]
* Arthropoda/Insecta: Drosophila [Locusta migratoria (migratory locust), Apis mellifera (honeybee)].

## Other variations

* Several arthropods translate the codon AGG as lysine instead of serine (as in the Pterobranchia Mitochondrial Code) or arginine (as in the standard genetic code).[8][9]
* GUG may possibly function as an initiator in Drosophila.[10][11] AUU is not used as an initiator in Mytilus[6]
* "An exceptional mechanism must operate for initiation of translation of the cytochrome oxidase subunit I mRNA in both D. melanogaster[12] and D. yakuba,[13] since its only plausible initiation codon, AUA, is out of frame with the rest of the gene. Initiation appears to require the "reading" of an AUAA quadruplet, which would be equivalent to initiation at AUA followed immediately by a specific ribosomal frameshift. Another possible mechanism ... is that the mRNA is "edited" to bring the AUA initiation into frame."[14]

## See also

* List of genetic codes

## References

This article incorporates text from the United States National Library of Medicine, which is in the public domain. [15]

1. ↑ Abascal, Federico; Posada, David; Knight, Robin D.; Zardoya, Rafael (2006-04-25). "Parallel Evolution of the Genetic Code in Arthropod Mitochondrial Genomes" (in en). PLOS Biology 4 (5): e127. doi:10.1371/journal.pbio.0040127. ISSN 1545-7885. PMID 16620150.
2. ↑ Telford, Maximilian J.; Herniou, Elisabeth A.; Russell, Robert B.; Littlewood, D. Timothy J. (2000-10-10). "Changes in mitochondrial genetic codes as phylogenetic characters: Two examples from the flatworms" (in en). Proceedings of the National Academy of Sciences 97 (21): 11359–11364. doi:10.1073/pnas.97.21.11359. ISSN 0027-8424. PMID 11027335.
3. ↑ "The mechanisms of codon reassignments in mitochondrial genetic codes". Journal of Molecular Evolution 64 (6): 662–88. June 2007. doi:10.1007/s00239-006-0284-7. PMID 17541678. Bibcode: 2007JMolE..64..662S.
4. ↑ "The mitochondrial genome of the honeybee Apis mellifera: complete sequence and genome organization". Genetics 133 (1): 97–117. January 1993. doi:10.1093/genetics/133.1.97. PMID 8417993.
5. ↑ 5.0 5.1 "Complete DNA sequence of the mitochondrial genome of the black chiton, Katharina tunicata". Genetics 138 (2): 423–43. October 1994. doi:10.1093/genetics/138.2.423. PMID 7828825. PMC 1206160. http://www.genetics.org/content/138/2/423.long.
6. ↑ 6.0 6.1 "A novel mitochondrial genome organization for the blue mussel, Mytilus edulis". Genetics 131 (2): 397–412. June 1992. doi:10.1093/genetics/131.2.397. PMID 1386586.
7. ↑ "Genome organization of Artemia mitochondrial DNA". Nucleic Acids Research 16 (14A): 6515–29. July 1988. doi:10.1093/nar/16.14.6515. PMID 3135541.
8. ↑ "Parallel evolution of the genetic code in arthropod mitochondrial genomes". PLOS Biology 4 (5): e127. May 2006. doi:10.1371/journal.pbio.0040127. PMID 16620150.
9. ↑ Robinson, Richard (25 April 2006). "For Arthropod Mitochondria, Variety in the Genetic Code Is Standard". PLOS Biology 4 (5): e175. doi:10.1371/journal.pbio.0040175. PMID 20076581.
10. ↑ "The mitochondrial DNA molecular of Drosophila yakuba: nucleotide sequence, gene organization, and genetic code". Journal of Molecular Evolution 22 (3): 252–71. 1985. doi:10.1007/BF02099755. PMID 3001325. Bibcode: 1985JMolE..22..252C.
11. ↑ "Nucleotide sequence of rat mitochondrial NADH dehydrogenase subunit 1. GTG, a new initiator codon in vertebrate mitochondrial genome". Nucleic Acids Research 16 (13): 6233. July 1988. doi:10.1093/nar/16.13.6233. PMID 3399396.
12. ↑ "Drosophila melanogaster mitochondrial DNA, a novel organization and genetic code". Nature 304 (5923): 234–41. 1983. doi:10.1038/304234a0. PMID 6408489. Bibcode: 1983Natur.304..234D.
13. ↑ "Nucleotide sequence of a segment of Drosophila mitochondrial DNA that contains the genes for cytochrome c oxidase subunits II and III and ATPase subunit 6". Nucleic Acids Research 11 (12): 4211–27. June 1983. doi:10.1093/nar/11.12.4211. PMID 6306579.
14. ↑ "Natural variation in the genetic code". Annual Review of Genetics 21: 67–91. 1987. doi:10.1146/annurev.ge.21.120187.000435. PMID 3327473.
15. ↑ Elzanowski, Andrzej; Ostell, Jim; Leipe, Detlef; Soussov, Vladimir. "The Genetic Codes". Taxonomy browser. National Center for Biotechnology Information (NCBI), U.S. National Library of Medicine. https://www.ncbi.nlm.nih.gov/Taxonomy/taxonomyhome.html/index.cgi?chapter=tgencodes#thetop.

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