Figure 3. Active site labeling of recombinant SmCL3 by the Clan CA cysteine protease affinity label ¹²⁵I-DCG-04.

(A) Purified enzyme incubated with ¹²⁵I-DCG-04. In order to confirm the specificity of the probe to the protease active site, enzyme was (B) incubated prior to labeling with the Clan CA inhibitor E-64, or (C) preheated at 70°C. Sample not incubated with the affinity probe (D). Samples were analyzed by SDS-PAGE (15%) and visualized in phosphor image mode.