FIG. 7.
Schematic model of the subunits of DmPBP (DmSNAPc) bound in alternative conformations to D. melanogaster U1 and U6 PSEAs. The model is based upon past (5, 33) and present data. The three subunits of the PSEA-binding protein are shown in the approximate relative positions where they interact with the phosphate backbone of the DNA. In each case, the DNA is bent similarly toward the face of the DNA that interacts with DmPBP45 (DmSNAP43) (5). If this is considered to be the upper face of the PSEA, DmPBP49 (DmSNAP50) interacts primarily with the front face of the 3′ half of the PSEA, and DmPBP95 (DmSNAP190) interacts primarily with the front face of the 5′ half of the PSEA but with the bottom face of the 3′ half of the PSEA.