Component of the ESCRT-I complex, a regulator of vesicular trafficking process. 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 (PubMed:14505570, PubMed:18005716). Interacts with TSG101, VPS37B, VPS37C, MVB12A and MVB12B (PubMed:14505570, PubMed:15218037, PubMed:18005716). 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 (PubMed:14505570, PubMed:21757351, PubMed:30929741). Interacts WITH VPS36; the interaction mediates the association with the ESCRT-II complex. Interacts with SNF8 and VPS25 (PubMed:18539118). Interacts with CEP55 (PubMed:17853893). Belongs to the VPS28 family.