Membrane-bound component of the endocytic receptor formed by AMN and CUBN. Required for normal CUBN glycosylation and trafficking to the cell surface. The complex formed by AMN and CUBN is required for efficient absorption of vitamin B12. Required for normal CUBN-mediated protein transport in the kidney. Interacts (via extracellular region) with CUBN/cubilin (PubMed:15845892). This gives rise to a huge complex containing one AMN chain and three CUBN chains (By similarity). Detected in kidney (at protein level). Detected in kidney and ileum. The complex formed by AMN and CUBN is composed of a 400 Angstrom long stem and a globular crown region. The stem region is probably formed by AMN and the CUBN N-terminal region, including the EGF-like domains. The crown is probably formed by the CUBN CUB domains. N-glycosylated. A soluble form arises by proteolytic removal of the membrane anchor. Defects in AMN are a cause of a canine form of megaloblastic anemia 1 (MGA1). The role of Amn in embryonic development seems to be species specific. In mice, null mutations lead to embryonic lethality. Canine mutations give rise to much milder symptoms.