Fig. 1

Functional elements of arrestins. a – Crystal structure of bovine ARRB1 colored according to the conserved exon-borders in vertebrates (rainbow coloring from exon 2 - red to exon 16 - dark violet). Exons 1, 15 as well as parts of exons 13, 14 and 16 are missing in the crystal structure (shown as dotted lines if not situated on the N- or C-terminus). Amino acids whose codons are split among two exons are shown in grey [112]. b – Schematic, linear representation of bovine ARRB1 with important functional elements shown in bright colors (orange - AP-2 binding site, light blue - three-element interaction, dark blue - polar core, green - finger loop, brown - high affinity IP6 binding site, pink - low affinity IP6 binding site, red - phosphate sensor, purple - clathrin binding sites). Arrestins encode two key domains, the arrestin_N domain (wheat) and the arrestin_C domain (light pink). Other regions that are present in the crystal structure are shown in light green, while sequence parts missing therein are shown in white. c – Functional elements depicted in B are mapped to the crystal structure of bovine ARRB1. The clathrin binding sites are missing in the crystal structure as they are situated on exons 13 and 15. PDB: 1G4R [55]. Crystal structure images were created with Pymol 1.8.4.0 Open-Source [113]