Cloning and sequencing of the gene for a Tetrahymena fimbrin-like protein

Tetrahymena F-actin-binding protein, which induces bundling of Tetrahymena F-actin, was localized to a division furrow during cytokinesis, We report h ere the cloning and characterization of the gene and cDNA of a Tetrahymena F-actin-binding protein. The cDNA encodes a protein comprising 579 deduced amino acids with a calculated molecular mass of 65.9 kDa. The predicted ami no acid sequence shares 37.7, 41.8, and 39% identity with the sequences of yeast fimbrin, Arabidopsis thaliana fimbrin, and Dictyostelium discoideum p lastin, respectively. The Tetrahymena F-actin-binding protein also shares t wo actin-binding domains previously identified in the fimbrin/plastin famil y, but lacks the EF-hand Ca2+-binding motif, suggesting that, this protein is a novel-fimbrin-like protein in Tetrahymena. Moreover, we cloned a genom ic DNA encoding the Tetrahymena fimbrin-like protein and performed Southern and Northern hybridizations, The results indicate that the genomic DNA pos sesses 9 introns and that both the gene and transcript of Tetrahymena fimbr in-like protein are single, Thus, we suggest that Tetrahymena fimbrin-like protein localizes to the division furrow and probably cross-links actin fil aments in a Ca2+-insensitive manner during cytokinesis.