CUBN: Cotransporter which plays a role in lipoprotein, vitamin and iron metabolism, by facilitating their uptake. Binds to ALB, MB, Kappa and lambda-light chains, TF, hemoglobin, GC, SCGB1A1, APOA1, high density lipoprotein, and the GIF-cobalamin complex. The binding of all ligands requires calcium. Serves as important transporter in several absorptive epithelia, including intestine, renal proximal tubules and embryonic yolk sac. Interaction with LRP2 mediates its trafficking throughout vesicles and facilitates the uptake of specific ligands like GC, hemoglobin, ALB, TF and SCGB1A1. Interaction with AMN controls its trafficking to the plasma membrane and facilitates endocytosis of ligands. May play an important role in the development of the peri-implantation embryo through internalization of APOA1 and cholesterol. Binds to LGALS3 at the maternal-fetal interface. Defects in CUBN are a cause of recessive hereditary megaloblastic anemia 1 (RH-MGA1); also known as MGA1 Norwegian type or Imerslund-Grasbeck syndrome (I-GS). RH-MGA1 is due to selective malabsorption of vitamin B12. Defects in vitamin B12 absorption lead to impaired function of thymidine synthase. As a consequence DNA synthesis is interrupted. Rapidly dividing cells involved in erythropoiesis are particularly affected.
Cellular Component: Golgi apparatus; lysosomal lumen; protein complex; brush border membrane; endoplasmic reticulum; lysosome; coated pit; membrane; apical part of cell; endocytic vesicle; apical plasma membrane; cytoplasm; brush border; endosome
Molecular Function: identical protein binding; protein binding; protein homodimerization activity; cobalamin transporter activity; hemoglobin binding; metal ion binding; receptor activity; calcium ion binding; cobalamin binding
Biological Process: steroid metabolic process; cholesterol metabolic process; receptor-mediated endocytosis; protein transport; in utero embryonic development; transport; lipoprotein transport; cobalamin transport; hemoglobin import; lipid metabolic process; response to nutrient
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