I know that FoldIt can handle 20 different amino-acids, and thought these were all which naturally exist in human cells.
But now I've read about Selenocysteine as 21st amino-acid (sometimes created by RNA Stop-Codon UGA), and want to know, why it is not available in the game.
Is someone here, who can explain this to me?
regards,
Alex
Foldit is based on the Rosetta engine, which can only handle the 20 standard amino acids by default. Thus, non-standard amino acids can only be handled with extra coding. In the case of selenocysteine, though, modeling it as regular cysteine is probably an adequate first approximation given that the only difference is the slightly larger selenium atom (versus a sulfur in cysteine).
That being said, structures containing selenocysteine are rare enough that it's probably not going to be a problem anyway (my RCSB protein data bank search only returned 18 results).
Thnks for the answer.