You may be interested in inteins, which are protein domains that spontaneously excise themselves from the host protein (the N and C terminal pieces of the host are left stitched together).
I think minimal inteins are usually 100-200 amino acids, and require quite specific residues positioned appropriately, so will not meaningfully affect the 20^100 number here. Nevertheless, it is an existence proof of the kind of activity you have in mind.
You may be interested in inteins, which are protein domains that spontaneously excise themselves from the host protein (the N and C terminal pieces of the host are left stitched together).
I think minimal inteins are usually 100-200 amino acids, and require quite specific residues positioned appropriately, so will not meaningfully affect the 20^100 number here. Nevertheless, it is an existence proof of the kind of activity you have in mind.