Component of the endosomal sorting complex required for transport-I (ESCRT-I) complex, a regulator of vesicular trafficking process. The ESCRT-I complex participates in the sorting of membrane proteins into vesicles that bud into late endosomal compartments called multivesicular bodies, and is also involved in the budding of many viruses. Component of the ESCRT-I complex (endosomal sorting complex required for transport I) which consists of TSG101, VPS28, a VPS37 protein (VPS37A to -D) and MVB12A or MVB12B in a 1:1:1:1 stoichiometry. Interacts with TSG101, VPS37B, VPS37C, MVB12A and MVB12B. Component of an ESCRT-I complex (endosomal sorting complex required for transport I) which consists of TSG101, VPS28, VPS37A and UBAP1 in a 1:1:1:1 stoichiometry. Interacts WITH VPS36; the interaction mediates the association with the ESCRT-II complex. Interacts with SNF8 and VPS25. Interacts with CEP55 (By similarity). Belongs to the VPS28 family.