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Abstract
Pyrrolysine is a lysine derivative encoded by the UAG codon in methylamine methyltransferase genes of Methanosarcina barkeri. Near a methyltransferase gene cluster is thepylT gene, which encodes an unusual transfer RNA (tRNA) with a CUA anticodon. The adjacent pylS gene encodes a class II aminoacyl-tRNA synthetase that charges the pylT-derived tRNA with lysine but is not closely related to known lysyl-tRNA synthetases. Homologs of pylS and pylT are found in a Gram-positive bacterium. Charging a tRNACUA with lysine is a likely first step in translating UAG amber codons as pyrrolysine in certain methanogens. Our results indicate that pyrrolysine is the 22nd genetically encoded natural amino acid.
↵* To whom correspondence should be addressed. E-mail: Krzycki.1{at}osu.edu
