Pyrrolysine

• N6- {[( 2R, 3R )-3 -methyl- 3,4- dihydro-2H- pyrrol- 2-yl] carbonyl} - L-lysine
• (2S )-2- amino-6- {[( 2R, 3R) -3-methyl - 3,4- dihydro-2H- pyrrole -2- carbonyl] -amino}- hexanoic acid

Fixed

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Pyrrolysine ( Pyl or O abbr. ) is a naturally occurring genetically encoded proteinogenic α -amino acid and a derivative of L- lysine. Pyrrolysine has three stereogenic centers ( carbons with four different substituents ). Hence there are eight possible stereoisomers. The biologically active isomer (see picture right) has the full name according to IUPAC: N6 -[( 2R, 3R )-3 -methyl-3 ,4-dihydro -2H -pyrrole-2 - ylcarbonyl ] - (S) -lysine. Since 15th October 2006, pyrrolysine is part of the protein alphabet of BLAST.

The side chain of pyrrolysine is lipophilic.

Pyrrolysine is considered by some archaea of the genera Methanosarcinales (eg Methanosarcina barkeri ) and two divergent bacteria (eg, Desulfitobacterium hafniense ) as part of enzymes of the methane metabolism used ( methylamine methyltransferases ). It is encoded by the UAG stop codon, whose normal function is modified by the presence of a particular gene sequence, thereby only the binding of the pyrrolysyl -tRNA to the ribosome is possible.

Evolution

Tribal History is not about the Pyrrolysinmaschinerie ( Pyl machinery ) is a new evolutionary achievement. On the contrary, because of the classification of the Pyl - aminoacyl- tRNA synthetase ( Pyl - aaRS ) for the senior class IIb, it is likely that the Pyl - aaRS from other aaRS sequences prior to cleavage of bacterial tribal line from the Archaea ( last common ancestor, MRCA: most recent common ancestor ) has emerged. This means that Pyl - aaRS very old.

Why very few organisms have the Pyl machinery, could be related to the fact that the genes were lost in all the other lines in the course of time. However, this is very unlikely.

A new interpretation assumes that the Pyl machinery originated by horizontal gene transfer from ( more ) Donorlinien that are extinct now, or have not yet been discovered. However, this also implies that the donor line, from which comes the Pyl machinery, had already reached a certain degree of diversity at the time, as even a common ancestor ( MRCA ) of our three kingdoms existed.