UNC-69 physically interacts with UNC-76, as shown by in vitro GST pull-down assays. (a) Full-length UNC-76 (UNC-76 FL) specifically binds to full-length GST-UNC-69 but not GST-CBP. The E1A-CBP interaction was used as a positive control. (b) Serial deletions of UNC-76: a portion of the carboxy-terminal region (deleted in UNC-76 Δγ but contained within UNC-76 B3 and A3) is necessary for interaction with GST-UNC-69. (c) Point mutation L287P or a small 19-amino-acid deletion (UNC-76 Δ19), which deletes amino acids 281–299, totally abolishes the ability of UNC-76 to bind GST-UNC-69. (d) Summary of the deletion analysis, as well as the results of rescuing experiments. Gray shading indicates conserved regions. Note that UNC-76 Δ19 not only loses its binding ability but also its rescuing activity for the unc-76(e911) mutants. The 19-amino-acid region (green) lies within a conserved region and overlaps with a region we predicted to form a coiled-coil domain (purple). A previously described axonal targeting sequence  is in red. The positions of different unc-76 alleles are indicated.