Tripeptidyl peptidase II (TPPII) is a crucial component of the proteolytic cascade acting downstream of the 26S proteasome in the ubiquitin-proteasome pathway. It is an amino peptidase belonging to the subtilase family removing tripeptides from the free N terminus of oligopeptides [1,2]. It consists of three main parts: the N-terminal subtilisin-like domain (Pfam:PF00082), a central domain and a C-terminal domain. The central domain consists of Ig-like subdomain (Pfam:PF12580) and a GBD-like one [2]. This is the C-terminal domain with adopts an ARM repeat fold [2].

1: Molecular architecture and assembly mechanism of Drosophila tripeptidyl peptidase II. Rockel B, Peters J, Muller SA, Seyit G, Ringler P, Hegerl R, Glaeser RM, Baumeister W; Proc Natl Acad Sci U S A. 2005;102:10135-10140. PMID:16006508

2: Hybrid molecular structure of the giant protease tripeptidyl peptidase II. Chuang CK, Rockel B, Seyit G, Walian PJ, Schonegge AM, Peters J, Zwart PH, Baumeister W, Jap BK; Nat Struct Mol Biol. 2010;17:990-996. PMID:20676100