Sap47 gene structure and protein isoforms. (A). Top: Exon-intron structure of the Sap47 gene of Drosophila melanogaster. Boxes represent exons 1 to 11, coding sequences are black. I-V: Five proposed splice isoforms of the Sap47 gene. The corresponding calculated molecular masses are given on the right. (B) Western blot analysis of head homogenates from wild type (WT, w1118) and Sap47 null mutant flies (control for specificity of signals). On the original blot 9 SAP47 bands can be identified as indicated on the left. Staining of cysteine string proteins (CSP) with monoclonal antibody ab49 serves as loading control.