Fig. 1. Molecular characterization of Drosophila Cas. (A) Organization of the DCas locus (DCas^P1: site of GAL4-containing P-element insertion). (B) Domain organization of human (H) and Drosophila (D) Cas proteins, and percentage amino acid identity of human Cas-family SH3-domains compared with DCas. (C) Alignment of the Drosophila and human Cas proteins, with conserved residues highlighted. In addition to the SH3 domain (black), tyrosine residues (blue), including those residing in consensus Crk/Nck SH2-binding sites (YXXP, also blue), and serine/threonine residues (purple) are conserved. Additional conserved regions include an SH3-domain-binding motif (yellow), a dimerization motif (black underline) and a Src-binding site (pYDYV, red underline).