The SEP domain is named after Saccharomyces cerevisiae Shp1, Drosophila melanogaster eyes closed gene (eyc), and vertebrate p47. In p47, the SEP domain has been shown to bind to and inhibit the cysteine protease cathepsin L [1]. Most SEP domains are succeeded closely by a UBX domain [1].

1: The SEP domain of p47 acts as a reversible competitive inhibitor of cathepsin L. Soukenik M, Diehl A, Leidert M, Sievert V, Bussow K, Leitner D, Labudde D, Ball LJ, Lechner A, Nagler DK, Oschkinat H; FEBS Lett 2004;576:358-362. PMID:15498563