Pore-forming peptides of Entamoeba dispar - Similarity and divergence to amoebapores in structure, expression and activity

Amoebapore, a 77-residue peptide with pore-forming activity from the human pathogen Entamoeba histolytica, is implicated in the killing of phagocytose d bacteria and in the cytolytic reaction of the amoeba against host cells. Previously, we structurally and functionally characterized three amoebapore isoforms in E. histolytica but recognized only one homolog in the closely related but non-pathogenic species Entamoeba dispar: Here, we identified tw o novel amoebapore homologs from E. dispar by molecular cloning. Despite st rong resemblance of the primary structures of the homologs, molecular model ing predicts a species-specific variance between the peptide structures. Pa rallel isolation from trophozoite extracts of the two species revealed a lo wer amount of pore-forming peptides in E. dispar and substantially higher a ctivity of the major isoform from E. histolytica towards natural membranes than that from E. dispar. Differences in abundance and activity of the lyti c polypeptides may have an impact on the pathogenicity of amoebae.