Figure 5. Peptide cleavage by the XPNPEP3 ortholog, ecAPP.

(A) Expression and purification of ecAPP. Coomassie staining of purified protein (lane 1) and immunoblot with anti-His tag antibody (lane 2) are shown. (B) Peptide substrates designed for enzymatic assay. Arrows indicate the cleavage site(s). Proline residue recognized by ecAPP is highlighted in red. Molecular weights are listed in Da. BN, bradykinin; N6, CEP290/NPHP6; AL, ALMS1; LR, LRRC50; DN, dynein. (C) Peptide cleavage detected by electrospray ionization–liquid chromatography–mass spectrometry. Mass spectrometry of peptides before and after digestion is shown. M+nH indicates the addition of n protons to the mass after ionization. intens, intensity.