Structural insights into the molecular ruler mechanism of the endoplasmic reticulum aminopeptidase ERAP1

Abstract

Endoplasmic reticulum aminopeptidase 1 (ERAP1) is an essential component of the immune system, because it trims peptide precursors and generates the N-termini of the finalMHCclass I-restricted epitopes. To examine ERAP1's unique properties of length-and sequence-dependent processing of antigen precursors, we report a 2.3 Å resolution complex structure of the ERAP1 regulatory domain. Our study reveals a binding conformation of ERAP1 to the carboxyl terminus of a peptide, and thus provides direct evidence for the molecular ruler mechanism.