Fig. 1. (A) Box diagram illustrating the primary structural features of formin family proteins in Dictyostelium discoideum. The deduced amino acid sequences of each gene are shown as open boxes. The gray boxes represent clusters of proline residues in each polyproline stretch within FH1 domains. The black boxes indicate the FH2 domains. forA, forB and forC were found as partial sequences encoded by cDNA clones in the Japanese cDNA database (FCL-AB11, SLB408 and SSC675, respectively). The accession numbers for full-length forA, forB and forC are AB082542, AB082543 and AB082544, respectively. forD, forE, forF, forG, forH and forI are found in contigs from the Dictyostelium genome database. The contig numbers are 16730, 16789, 17584, 16652, 15079 and 14500, respectively. (B) The predicted amino acid sequence of the forC gene product. Three highly conserved regions within the FH3 domain are shaded in gray. The FH2 domain is shown by white letters on a black background. (C,D) Amino acid sequence alignment of the FH2 (C) and FH3 (D) domains of various formin homologues. Multiple sequence alignments were performed using ClustalW 1.8 and colored with BOXSHADE. Residues identical to the column consensus are shown on black backgrounds; residues similar to the column consensus are shown on gray backgrounds. (C) Eleven proteins are compared: from top to bottom: Dictyostelium discoideum ForC, ForA and ForB; mouse p140mDia (mDIA1) (Watanabe et al., 1997); human hDia1 (DFNA1) (Lynch et al., 1997); hDia2 (Bione et al., 1998); Drosophila melanogaster Diaphanous (Castrillon and Wasserman, 1994); Caenorhabditis elegans Cyk-1 (Swan et al., 1998); mouse Formin (Chan et al., 1996; Woychik et al., 1990); Saccharomyces cerevisiae Bni1 (Jansen et al., 1996; Zahner et al., 1996); and Schizosaccharomyces pombe Cdc12 (Chang et al., 1997). (D) Twelve proteins are aligned: from top to bottom: Dictyostelium discoideum ForC, ForA and ForB; mouse p140mDia; human hDia2; Drosophila melanogaster Diaphanous and Cappuccino (Emmons et al., 1995); Caenorhabditis elegans Cyk-1; mouse Formin; Saccharomyces cerevisiae Bni1; Schizosaccharomyces pombe Cdc12; and human FHOS (Westendorf et al., 1999). The reported conserved regions (Petersen et al., 1998) are indicated by solid underlines. A newly found conserved region in the third domain is indicated by a dashed underline.