Structure of stonins and related proteins. (A) Schematic representation of human stonin 1 (Hs Stn1, GenBank/EMBL/DDBJ accession no. AF255310), human stonin 2 (Hs Stn2, AF255309), D. melanogaster stoned B (Dm STNB, U54982), C. elegans hypothetical protein C27H6.1 (Ce C27H6.1, Z81042), and the human μ2 subunit of the AP-2 complex (Hs μ2, NM_004068). Specific domains of homology are color coded and denoted as follows: PRD, proline-rich domain; SHD, stonin homology domain; MHD, μ-homology domain; BBD, β-binding domain. Black lines denote regions with no significant sequence homology. Numbers of NPF or DPF motifs in the PRDs are indicated. (B) Alignment of short sequences in the PRD of human stonin 2 with homologous sequences in human (Hs) epsin 1 (AF073727), epsin 2 (AF062084), and amphiphysin 2 (AAB63263). Identical residues are boxed, and NPF motifs are highlighted in yellow. (C) Multiple sequence alignment of the SHD and MHD domains of stonin family members. The black and gray boxes indicate identical and strongly conserved amino acids, respectively. Blue and orange dots indicate amino acids in μ2 that are involved in binding YXXØ-type signals () and the C2B domain of synaptotagmin I (), respectively. Numbers denoting the last amino acid in each sequence are indicated on the right.