Component of the ESCRT-I complex, a regulator of vesicular trafficking process. Required for the sorting of endocytic ubiquitinated cargos into multivesicular bodies (By similarity). 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; the association appears to be mediated by the TSG101-VPS37 binary subcomplex. Interacts with VPS28. Interacts with VPS37B; the association appears to be mediated by the TSG101-VPS37 binary subcomplex. Interacts with VPS37C; the association appears to be mediated by the TSG101-VPS37 binary subcomplex (By similarity). Belongs to the MVB12 family.