[priyasaravanan_1406]

Amino acid: Pyrrolysine

Year of discovery: 2002

Abbreviation: Pyl

In short: O

Position in the standard amino acid list: 22nd Amino acid next to Selenocysteine

Codon: UAG, which is actually a stop codon but codes for the amino acid Pyrrolysine in the presence of PYLIS element.

PYLIS: Pyrrolysine Insertion sequence found in some mRNA as a stem loop structure and when UAG codon is followed by this structure it will signal the production of the amino acid Pyrrolysine instead of the actual terminating function of the codon.

Found in the Organism: Methanosarcinaceae barkeri (Archaea species)

First Located: In methyl transferase enzyme’s active site and hence Pyrrolysine makes its significance in most of the methane producing pathways.

Some of the enzymes containing Pyrrolysine: Methyltransferases MtmB, MtbB and Mttb

Structure: Methylated pyroline carboxylate is bridged to the amino group of L- Lysine where the amide group acts as the bridge.

Chemical formula: C12H21N3O3

Side chain: -(CH2)4NHCOC4H5NCH3

pH: Pyrrolysine is a weak Basic

Presence in human proteins: 0 percent

Bioproduction of Pyrrolysine: The synthesis of Pyrrolysine requires two molecules of the amino acid L- Lysine. One molecule transforms into Methylornithine before binding itself to the second molecule which is followed by several steps like deamination and cyclization resulting in the formation of the amino acid Pyrrolysine.

Genes involved in the synthesis of Pyrrolysine and its incorporation into proteins are pylT, pylS, pylB, pylC, pylD.

pylT: pylT which encodes tRNA is an important unit in the decoding of the codon UAG into the aminoacid Pyrrolysine.

pylS: This gene codes for pyrrosyl t-RNA synthetase which charges the pylT encoded tRNA with Pyrrolysine (tRNApyl).

In a research study the recombinant E.coli carrying the genes pylT, pylS, pylB, pylC and pylD derived from methanogenic archaea has been observed for the insertion of the synthesized pyrrolyisne into the proteins.