Fig. 1. Sbf1 is a unique member of the myotubularin family of phosphatases. (A) Schematic representation of Sbf1 and myotubularin-related proteins. A highly conserved region that spans the PTP consensus motif is indicated by black rectangles; PTP motifs containing germline mutations are indicated with half white/half black rectangles. Gray oval in Sbf1 indicates CRS domain conserved in various signaling proteins. Gray box at Sbf1 N terminus denotes 80 amino acids of additional similarity with the N terminus of Rab3GEF. Start and stop codons are indicated in proteins where they are known. (B) Sequence alignment of the N-terminal CRS domain in Sbf1 reveals similarity with several known and hypothetical proteins. Black boxes indicate identical residues; shaded boxes indicate conservative amino acid substitutions. AA481292, AL161790 and AI158686 are unique human or mouse ESTs. C12714 is a predicted C. elegans protein. Sequences for CRAG, ST5, Rab3GEF, Rab6BP have been reported previously (Xu et al., 1998; Janoueix-Lerosey et al., 1995; Wada et al., 1997). (C) Anti-Sbf1 western blot analysis of NIH 3T3 cells stably transfected with wild-type Sbf1 or vector alone.