Cleavage of purified, functionally active CD11b/CD18 by PMN serprocidins. (A) Binding of PMN serprocidins with purified CD11b/CD18. (B) Binding of PMN serprocidins and azurocidin with purified CD11b/CD18 (20 μg/mL) in the presence or absence of various inhibitors. (C) Correlation between NE-CD11b/CD18 binding and CRBM1/5-CD11b/CD18 binding. In this experiment, CD11b/CD18 was first immobilized onto the plates, incubated with NE and fluorescently labeled CBRM1/5. (D) Specific cleavage of purified, functionally active CD11b/CD18 by the 3 leukocyte serprocidins, but not by MMP-9. (E) Identification of the cleavage site of NE, NPR-3 and NCG on CD11b. (Left panel) Gelcode staining of the cleavage of purified CD11b by serprocidins. (Top panel) The N-terminal peptide sequence of the ∼ 60 kD CD11b fragment cleaved by NE, NPR-3, and NCG, respectively. (Bottom panel) The location of the cleavage sites within the extracellular domain of CD11b. Note that NE and NPR-3 cleave CD11b at the same site between ⁷⁶¹Thr-Ala⁷⁶³ (red arrow), while NCG cleaves CD11b between ⁷⁶⁰Phe-Thr⁷⁶¹ (blue arrow). Data represent the mean ± SD of 3 independent experiments, each performed in triplicate. *P < .05; **P < .01.