Cubilin and AMN form the cubam complex; AMN binds the amino-terminal third of cubilin and directs the subcellular localization and endocytosis of cubilin with its ligand. Neither protein alone confers ligand endocytosis; together they reconstitute IF-cobalamin uptake and lysosomal degradation.

Proteomic profiling of human urinary exosomes; AMN is among detected proteins, consistent with shedding of apical renal-epithelial membrane proteins.

AMN provides membrane anchorage and endocytic capacity via two redundant FXNPXF cytoplasmic signals that engage the clathrin adaptors ARH and Dab2 to internalize cubam and its ligands.

AMN-dependent glycosylation and trafficking are required for cell-surface expression of cubilin; IGS-causing AMN missense mutations cause ER retention and abolish surface expression of cubilin.

Crystal structure of AMN with the amino-terminal region of cubilin shows a single AMN chain anchoring three ligand-binding cubilin subunits to the membrane via a beta-helix-beta-helix docking.

AMN is a single-pass type I membrane glycoprotein localized to the apical cell membrane; it is the membrane-bound component of the AMN+CUBN endocytic receptor. A soluble form arises by proteolytic removal of the membrane anchor.