In 1991, I found these weird intervening sequences in Vent DNA polymerase. They were unlike any known intron and were in-frame with the surrounding sequences. So, I went to the RNA Processing Meeting in 1991 looking for answers. I remember sitting on the little stone wall outside the auditorium speaking with everyone who would listen, especially Marlene Belfort. Could these elements splice as proteins and not as RNA? In 1993 we proved that splicing was at the protein level. As they say, the rest is intein history. Thanks CSH!
http://www.neb.com/neb/inteins.html