Fig. 2. Structure and expression of Bchs protein. (A) The domains of Drosophila Bchs and human Alfy are similar in organization and sequence. The percentage amino acid identity between domains is indicated, including homology for the extended portion of the protein called CRAB (Conserved Region in Alfy and Bchs; shown in gray and not shown to scale to conserve space). Mutations in bchs alleles are marked (nonsense, stars; missense, triangles). (B) In a stage 13 embryo, bchs mRNA is highly expressed in embryonic CNS, including brain and ventral nerve cord, and in the salivary glands (arrowhead). A sense control probe showed no signal above background (data not shown). (C) Analysis of murine mRNA indicates mouse Alfy is widely expressed, but enriched in adult brain. (D) Protein blot probed with antisera raised to amino acids 2237-2590 of Bchs (arrow indicates Bchs; just below Bchs, the anti-sera also detects a crossreacting protein, whose size and intensity are unaffected in multiple bchs truncation alleles). GMR-GAL4;EP-bchs animals express more Bchs protein than controls, including EP-bchs. Overexpression is abolished by the nonsense mutation in bchs¹⁷ (GMR-GAL4;bchs¹⁷/+). bchs¹², bchs¹⁷ and bchs⁵⁸ express no detectable Bchs, while bchs⁸ still produces substantial amounts of protein. Antibody against Elav demonstrates equal loading. VNC, ventral nerve cord.