Fig. 1. Alignment of human and D. discoideum SBDS proteins. The boundaries of the three major domains in SBDS and related orthologs include: an N-terminal module with two motifs, SHHP1 and SHHP2; a central tri-helical bundle module; and a C-terminal module with RNA-recognition motif (RRM-like). The four ß strands (E-runs) and four helices (H-runs) in the N-terminal module, and the unique 24-residue tail of the Dictyostelium SBDS ortholog are indicated.