The Endosomal Sorting Complex Required for Transport (ESCRT) complexes form the machinery driving protein sorting from endosomes to lysosomes. ESCRT complexes are central to receptor down-regulation, lysosome biogenesis, and budding of HIV. Yeast ESCRT-I consists of three protein subunits, Vps23, Vps28, and Vps37. In humans, ESCRT-I comprises TSG101, VPS28, and one of four potential human VPS37 homologues. The assembly of the ESCRT-I complex is directed by the C-terminal steadiness box (SB) of VPS23, the N-terminal half of VPS28, and the C-terminal half of VPS37. The structure is primarily composed of three long, parallel helical hairpins, each corresponding to a different subunit. This entry represents the N-terminal domain of Vps28 PMID:16615893,PMID:16615894.