Fig. 3.

Altered N-terminal peptide trimming by the AS associated ERAP1 K⁵²⁸R mutant. (A) Extracted ion chromatograms (EIC) of the peptide cleavage product TANRELIQQEL after trimming of QITANRELIQQEL by ERAP1 wild type and the K⁵²⁸R mutant. Peptide precursor and enzymes were incubated for different sampling times revealing differential kinetic activity between both variants. (B) Relative quantitation of the EICs for the substrate peptide QITANRELIQQEL shows higher activity of the ERAP1 wild type. The intermediate product TANRELIQQEL is further processed by ERAP1 wild type while the K⁵²⁸R variant stops processing this peptide at the 11-mer stage. (C) Relative quantitation of the EICs for all observed peptide intermediates. While the wild type reaches equilibrium at the 8- and 9-mer, the K⁵²⁸R variant stops processing the 11-mer.