Cubilin is an endocytic receptor that lacks a classical transmembrane region. It is a multidomain receptor that contains an amino terminal 110 residue segment followed by 8 epidermal growth factor (EGF)-like repeats and a contiguous stretch of 27 CUB domains. Cubilin acts as a receptor for intrinsic factor-vitamin B12 complexes. Cubilin is located within the epithelium of intestine and kidney. Cubilin co-localizes with and binds to Megalin, a 600kDa member of the LDL receptor family that is required for the internalization of cubilin-bound ligands, such as vitamin B12, apolipoprotein A1 and Albumin. Megalin specifically binds to cubilin in the amino terminal region that contains the EGF-like repeats and CUB domains 1 and 2. Mutations in Cubilin may play a role in autosomal recessive megaloblastic anemia also known as Imerslund-Grasbeck’s disease, which causes intestinal malabsorption of vitamin B12.