THE BASIC ISOFORM OF PROFILIN IN PATHOGENIC ENTAMOEBA-HISTOLYTICA - CDNA CLONING, HETEROLOGOUS EXPRESSION, AND ACTIN-BINDING PROPERTIES

In the human parasite Entamoeba histolytica, components of the cytoske leton are involved in the pathogenicity by their contribution to immun e evasion by antibody capping and shedding. In this study, we focus on profilin as a central regulatory component of the cytoskeleton. Profi lin was isolated from trophozoites of the pathogenic E. histolytica st rain SFL-3, and partial amino acid sequences were used to devise a pro be for isolating a profilin cDNA. The deduced complete primary structu re was divergent: plant profilins with amino acid sequence identities in the range 33-38% were more closely related than the mammalian profi lins with sequence identities 21-28%. The cDNA was expressed as a nonf usion protein in Escherichia coli. Isoelectric focussing of the natura l profilin isolated from E. histolytica showed two isoforms with diffe rent isoelectric points; the recombinant profilin migrated with the ba sic isoform. In a blot overlay experiment, purified I-125-labeled reco mbinant profilin bound not only to plant actin, but also to mammalian actin, demonstrating that cytoskeletal components from distantly relat ed organisms with divergent primary structures can be compatible.