There is also selenocysteine, which is cys with the sulfur replaced by selenium. https://en.wikipedia.org/wiki/Selenocysteine https://en.wikipedia.org/wiki/Sel

There is also selenocysteine, which is cys with the sulfur replaced by selenium. https://en.wikipedia.org/wiki/Selenocysteine https://en.wikipedia.org/wiki/Selenocysteine It's not present in all organisms, but where it is, it is incorporated in proteins during translation, not after.