Stands for in
- or int
, come to think of it. Internal to another protein
, that is. One that is splice
d out of the outer protein (the extein
) to produce a mature
host protein and a free intein.
This might seem a little bizarre, but that's biology for you. It is as if a 'virus-like' protein is embedded in a larger one. It is more precise to say that a protein does some autoprocessing on an internal, rather than a terminal, sequence. The obvious analogy is with introns in genes, although the intein gene is probably not an intron!
There is a database of inteins at: