CLONING AND CHARACTERIZATION OF ACTIN DEPOLYMERIZING FACTOR FROM TOXOPLASMA-GONDII

We determined the predicted amino acid sequence of actin depolymerizin g factor (ADF) from Taxoplasma gondii by sequencing the full-length cD NA. T. gondii ADF consists of 118 amino acids (calculated molecular we ight 13400) and shares a high degree of sequence similarity to other l ow molecular weight actin monomer sequestering proteins, especially Ac anthamoeba actophorin, plant ADFs and yeast and vertebrate cofilin. AD F from T. gondii is smaller and does not contain a nuclear localizatio n sequence like the related vertebrate proteins. Southern blot analysi s indicates that T. gondii ADF is a single-copy gene. Homogeneous reco mbinant T. gondii ADF purified from E. coli is active in binding actin monomers and depolymerizing F-actin. Localization of ADF by immunoflu orescence and immuno-electron microscopy indicates ADF is scattered th roughout the cytoplasm and prominently localized beneath the plasma me mbrane in T. gondii. (C) 1997 Elsevier Science B.V.