2018 - Emerging Topics in Life Sciences


The 22nd amino acid discovered to be directly encoded, pyrrolysine, is specified by UAG.
Until recently, pyrrolysine was only known to be present in archaea from a methanogenic
lineage (Methanosarcinales), where it is important in enzymes catalysing anoxic methylamines
metabolism, and a few anaerobic bacteria. Relatively new discoveries have
revealed wider presence in archaea, deepened functional understanding, shown remarkable
carbon source-dependent expression of expanded decoding and extended exploitation
of the pyrrolysine machinery for synthetic code expansion. At the same time, other
studies have shown the presence of pyrrolysine-containing archaea in the human gut and
this has prompted health considerations. The article reviews our knowledge of this
fascinating exception to the ‘standard’ genetic code.

Brugère J.-F., Atkins J.F., O’Toole P.W., Borrel G. 
Pyrrolysine in Archaea, a 22nd amino acid encoded through a genetic code expansion. Emerging Topics Life Sciences, 2018: ETLS20180094.