Fig. 2. Schematic diagram depicting the domain organization of Alix and its family members in yeast, Bro1 and Rim20. Alix in humans contains 868 amino acid residues and is 94% identical to mouse Alix, which has 869 residues. Bro1 is similar in length (844 residues) and domain organization, whereas Rim20 is shorter (661 residues) and lacks a C-terminal proline-rich (Pro) region. Based upon the structure of the Bro1 domain in Bro1 (Kim et al., 2005), the Bro1 domains of Alix and Rim20 are predicted to span residues 1-366 and 1-387, respectively. Two putative coiled-coil domains (CC) are located between residues 430-471 and residues 543-583 of Alix, whereas Bro1 and Rim20 are each predicted to have a single CC domain between residues 543-583 (in Bro1) and 386-426 (in Rim20). The proline-rich region of Alix has the majority of protein-binding sites that link it to various cellular mechanisms (see Table 1 for details on specific amino acids involved in protein interactions). Similarly, the proline-rich region of Bro1 is contained within a region required for interaction with Doa4 (Kim et al., 2005). The C-terminal region of Rim20 binds the Rim101 transcription factor (Xu and Mitchell, 2001).