Fig. 6. The AIP1 deletion mutant AIP1-717-784 shows reduced binding to SETA. (A) The C-terminal proline-rich region containing multiple P-x-x-P motifs between residues 717 and 869 (black vertical lines) in full-length AIP1, and regions deleted in two AIP1 mutants AIP1-784Stop and AIP1-717-784. (B) In vitro binding assays were performed with bacterial GST-SETA fusion proteins encoding either isolated SH3 domains (SH3-1, -2 and -3) or full length SETA (123cc), and in vitro transcribed and translated, radiolabeled, full-length or mutant AIP1. Full-length AIP1 bound to the middle SH3-2 domain, and more strongly to full length SETA, as shown previously (Chen et al., 2000). AIP1-784Stop showed a similar binding profile to full-length, while AIP1-717-784 showed faint, non-specific binding, indicating that the N-terminal half of the P-x-x-P domain mediated SETA binding.