Project Summary
Endoplasmic reticulum aminopeptidase 1 (ERAP1) and insulin-regulated aminopeptidase (IRAP) belong to
the oxytocinase subfamily of M1 aminopeptidases (M1APs), which are a diverse family of metalloenzymes
involved in a wide range of functions including cell maintenance, development, and immune defense, and have
been implicated in various chronic and infectious diseases of humans. Structure and mechanism of the
conserved catalytic domain, termed peptidase_M1 domain, have been well studied. As a result, many research
groups have begun assessing their potential as therapeutic targets for various diseases, such as cancer,
autoimmunity, Alzheimer's and Parkinson's diseases, hypertension, and viral infections. However, targeting any
M1AP to treat human diseases is complicated because there are nine characterized and closely related M1APs
in humans. This poses a dilemma situation to deal with off-target side effects. Nonetheless, current inhibitor-
developing strategies rely heavily on Bestatin derivatives or phosphinic pseudopeptides to occupy the S1 and/or
S1’ binding pockets of the highly conserved peptidase_M1 site. Although potent, these inhibitors also inhibit
many other essential M1AP members, lead to undesired side effects. Our lab has previously determined a novel
ERAP1 C-terminal regulatory domain structure, now classified as the ERAP1_C like domain. This ERAP1_C
fold, separated from the conserved peptidase_M1 domain, is found in all available structures of the M1AP family,
but their sequences vary substantially among family members, likely to harbor distinct specificity subsites.
Indeed, our recent results on four structures of ERAP1_C domain in complex with various substrate C-termini
have revealed specificity subsites (e.g., SC’ subsite) embedded in this ERAP1_C domain to recognize ERAP1-
specific anchor residue at the substrate carboxyl-end, a critical feature of ERAP1 to act as a molecular ruler in
generating antigens with a correct size. We thus hypothesize that each M1AP carries distinct specificity subsites
in its special version of ERAP1_C domain to accommodate distal parts of their cognate substrates. To test this
hypothesis, we propose in this R15 project to investigate structural details of IRAP specificity subsites for
recognizing the distal ends of its cognate substrates, and to exploit newly identified specificity subsites for
targeted screenings to identify modulators that are both potent and selective against ERAP1 or IRAP over other
M1APs. The proposed research will provide insights into both common and distinct interactions between
specificity subsites of different M1APs and their cognate substrates, and is thus critical to improve our capability
to develop specific and selective modulators or inhibitors to fight against pathogens or chronic diseases.
Furthermore, this AREA research will provide continuous research opportunities for undergraduate and graduate
students at UMass Lowell, and help the University to enhance its research environment.