Primary structures of Homer family proteins. The conserved amino-terminal EVH1-like domain (which shows 80% sequence similarity between family members) is in yellow. The conserved region of Homer1 (CRH1)  and a proline motif (P-motif, 138-Ser-Pro-Leu-Thr-Pro-142) is specific to the mammalian Homer1 subfamily. The carboxy-terminal regions contain coiled-coil and leucine zipper structures and show only 30% sequence similarity among the family members. The coiled-coil regions are in orange, green and pink for the Homer1, Homer2, and Homer3 alternatively spliced forms, respectively. The leucine zipper structures, as predicted by Sun et al. , are shown as LzipA and LzipB in gray. The nomenclature is from Soloviev et al. , Saito et al. , Bottai et al.  and Klugmann et al. . Homer3axx and Homer3bxx represent the products of four alternative splicing variants, where xx can be 00, 01, 10, or 11 to show the combination of two three-amino-acid insertions (purple) in the coiled-coil domain, as has been suggested for the human forms . Residues involved in ligand contacts are colored light blue.