glutamine (and its derivatives) could still be present in the cell and used as an amide donor. Our results show that its incorporation into the code was late but that does not necessarily mean it was absent.

Order of amino acid recruitment into the genetic code resolved by last universal common ancestor’s protein domains | PNAS The current “consensus” order in which amino acids were added to the genetic code is based on potentially biased criteria, such as the absence of s...

We identified protein domains in LUCA (Last Universal Common Ancestor). Their distinctive amino acid usage reveals the order amino acids were added to the genetic code, based mostly on size. Older proteins hint at earlier alternative codes. 1/15 @seekingluca.bsky.social www.pnas.org/doi/10.1073/...