Identification of EhICP1, a chagasin‐like cysteine protease inhibitor of Entamoeba histolytica

Abstract
Based on the Entamoeba histolytica genome project (www.sanger.ac.uk/Projects/E_histolytica/) we have identified a cysteine protease inhibitor, EhICP1 (amoebiasin 1), with significant homology to chagasin. Recombinant EhICP1 inhibited the protease activity of papain and that of a trophozoite lysate with Ki’s in the picomolar range. By immunocytology, we localized the endogenous ∼13kDa EhICP1 in a finely dotted subcellular distribution discrete from the vesicles containing the amoebic cysteine protease, EhCP1 (amoebapain). In an overlay assay, we observed binding of recombinant EhICP1 to EhCP1. As a heptapeptide (GNPTTGF) corresponding to the second conserved chagasin motif inhibited the protease activity of both papain (Ki 1.5μM) and trophozoite extract (Ki in sub-mM range), it may be a candidate for the rational development of anti-amoebiasis drugs