Pyrrolysine
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| Surname | Pyrrolysine | |||||||||
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| Molecular formula | C 12 H 21 N 3 O 3 | |||||||||
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| Molar mass | 255.31 g · mol -1 | |||||||||
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firmly |
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| As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . | ||||||||||
Pyrrolysine (abbr. Pyl or O ) is a naturally occurring, genetically coded proteinogenic α - amino acid and a derivative of L - lysine . Pyrrolysine has three stereogenic centers (carbon atoms with four different substituents). So there are eight possible stereoisomers . The biologically active isomer (see picture on the right) has the full name according to IUPAC : N 6 - [(2 R , 3 R ) -3-methyl-3,4-dihydro- 2 H -pyrrol-2-ylcarbonyl] - ( S ) -lysine. Pyrrolysine is also known as the 22nd proteinogenic amino acid; its letter symbol “O” has been part of the BLAST protein alphabet since 2006 .
The side chain of pyrrolysine is lipophilic .
Translation
Pyrrolysine is one of the non-canonical proteinogenic amino acids that are genetically encoded and naturally occur as a protein building block in living beings when inserted during translation .
In some methanogenic species of archaea of the family Methanosarcinaceae (. E.g., Methanosarcina barkeri and individual) bacterial species (. Eg Desulfitobacterium hafniense ) is pyrrolysine component of enzymes of the methane - metabolism (methylamine methyl). These organisms have a tRNA Pyl as well as a pyrrolysyl- tRNA synthetase specific for their loading and can thus insert pyrrolysine into the ribosome during translation .
Functions as a codon for this proteinogenic amino acid UAG, the usual function of which as a stop codon is suppressed. This is in some Archaeenarten apparently facilitated with specific sequences in the context of the transcript that the formation of hairpin structures lead the mRNA as a so-called PYLIS element (a py rrolysine i nsertion s equence). The name was chosen on the assumption of a functional similarity with the Secis element, which plays an important role in the recoding of another stop codon ( UGA ) for the incorporation of selenocysteine as a proteinogenic amino acid. But here an effective translation of the UAG triplet into pyrrolysine is apparently also possible without reinforcement by such cis-acting contextual elements - in addition to the expiry of a termination .
evolution
In tribal history , the pyrrolysin machinery (Pyl machinery) is not a new evolutionary achievement. On the contrary, because of the classification of the Pyl- aminoacyl-tRNA synthetase (Pyl-aaRS) in the older class IIb, it is likely that the Pyl-aaRS from other aaRS sequences before the cleavage of the bacterial lineage from that of the archaea (last common Ancestor, MRCA: most recent common ancestor ). This means that Pyl-aaRS are very old.
The reason why very few organisms have the Pyl machinery could be related to the fact that the genes in all other lines were lost over time. However, this is very unlikely.
A new interpretation assumes that the Pyl machinery stems from horizontal gene transfer from (several) donor lines that have since become extinct or have not yet been discovered. However, this also assumes that the donor line from which the Pyl machinery originates had already achieved a certain degree of diversity at the time when a common ancestor (MRCA) of our three kingdoms still existed.
literature
- Fournier, G. (2009): Horizontal gene transfer and the evolution of methanogenic pathways . In: Methods Mol Biol . 532; 163-179; PMID 19271184 ; doi : 10.1007 / 978-1-60327-853-9_9
- Srinivasan, G. et al. (2002): Pyrrolysine encoded by UAG in Archaea: charging of a UAG-decoding specialized tRNA. In: Science. 296 (5572), pp. 1459-1462 PMID 12029131 doi : 10.1126 / science.1069588
- Hao, B. et al. (2002): A new UAG-encoded residue in the structure of a methanogen methyltransferase. In: Science. 296 (5572), pp. 1462-1466. PMID 12029132 doi : 10.1126 / science.1069556
- Fenske, C. et al. (2003): How unique is the genetic code? In: Angewandte Chemie. 115 (6), pp. 626-630. doi : 10.1002 / anie.200390142
Individual evidence
- ↑ This substance has either not yet been classified with regard to its hazardousness or a reliable and citable source has not yet been found.
- ↑ Release Notes of BLAST v2.2.15 ( Memento of the original from March 10, 2016 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ D. Longstaff, S. Blight, L. Zhang, K. Green-Church, J. Krzycki: In vivo contextual requirements for UAG translation as pyrrolysine. In: Molecular Microbiology , Volume 63, No. 1; January 2007, pp. 229-241; PMID 17140411 , doi : 10.1111 / j.1365-2958.2006.05500.x
- ↑ Fournier, G. (2009): Horizontal gene transfer and the evolution of methanogenic pathways . In: Methods Mol Biol . 532; 163-179; PMID 19271184 ; doi : 10.1007 / 978-1-60327-853-9_9
