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Pyrrolysine and selenocysteine use dissimilar decoding strategies.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 2005 May 27; Vol. 280 (21), pp. 20740-51. Date of Electronic Publication: 2005 Mar 22. - Publication Year :
- 2005
-
Abstract
- Selenocysteine (Sec) and pyrrolysine (Pyl) are known as the 21st and 22nd amino acids in protein. Both are encoded by codons that normally function as stop signals. Sec specification by UGA codons requires the presence of a cis-acting selenocysteine insertion sequence (SECIS) element. Similarly, it is thought that Pyl is inserted by UAG codons with the help of a putative pyrrolysine insertion sequence (PYLIS) element. Herein, we analyzed the occurrence of Pyl-utilizing organisms, Pyl-associated genes, and Pyl-containing proteins. The Pyl trait is restricted to several microbes, and only one organism has both Pyl and Sec. We found that methanogenic archaea that utilize Pyl have few genes that contain in-frame UAG codons, and many of these are followed with nearby UAA or UGA codons. In addition, unambiguous UAG stop signals could not be identified. This bias was not observed in Sec-utilizing organisms and non-Pyl-utilizing archaea, as well as with other stop codons. These observations as well as analyses of the coding potential of UAG codons, overlapping genes, and release factor sequences suggest that UAG is not a typical stop signal in Pyl-utilizing archaea. On the other hand, searches for conserved Pyl-containing proteins revealed only four protein families, including methylamine methyltransferases and transposases. Only methylamine methyltransferases matched the Pyl trait and had conserved Pyl, suggesting that this amino acid is used primarily by these enzymes. These findings are best explained by a model wherein UAG codons may have ambiguous meaning and Pyl insertion can effectively compete with translation termination for UAG codons obviating the need for a specific PYLIS structure. Thus, Sec and Pyl follow dissimilar decoding and evolutionary strategies.
- Subjects :
- Amino Acid Sequence
Archaea chemistry
Archaea genetics
Archaea metabolism
Archaeal Proteins chemistry
Archaeal Proteins genetics
Archaeal Proteins metabolism
Codon, Terminator genetics
Conserved Sequence
DNA Transposable Elements genetics
Lysine metabolism
Methanosarcina chemistry
Methanosarcina genetics
Methanosarcina metabolism
Methanosarcinaceae chemistry
Methanosarcinaceae genetics
Methanosarcinaceae metabolism
Methylamines metabolism
Methyltransferases chemistry
Methyltransferases metabolism
Molecular Sequence Data
Operon genetics
Phylogeny
Selenocysteine metabolism
Sequence Alignment
Codon genetics
Lysine analogs & derivatives
Lysine genetics
Selenocysteine genetics
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 280
- Issue :
- 21
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 15788401
- Full Text :
- https://doi.org/10.1074/jbc.M501458200