title: The binding properties of the human receptor for the cellular uptake of vitamin B12.
abstract: Cellular uptake of vitamin B(12) (cobalamin, Cbl) is mediated by a receptor expressed on the plasma membrane that binds transcobalamin (TC) saturated with Cbl and internalizes the TC-Cbl by endocytosis. A few reports have described the characterization of the receptor protein. However, many discrepancies have emerged in the functional and structural properties of the receptor and therefore, the identity and primary structure of this protein remains unconfirmed. In this report, we provide evidence of a 58 kDa monomeric protein as the likely receptor for the uptake of TC-Cbl and that the functional activity is not associated with a 72/144 kDa monomer/dimer with immunoglobulin Fc structural domain that has been purported to be the receptor in a number of publications.
authors.affiliation: Department of Biochemistry, SUNY-Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA. edward.quadros@downstate.edu
authors.forename: Edward V
authors.initials: EV
authors.lastname: Quadros
authors.forename: Yasumi
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Sequeira
mesh_terms: D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004492:Edetic Acid / Q000494:pharmacology; D006801:Humans; D008970:Molecular Weight; D009419:Nerve Tissue Proteins / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000737:chemistry / Q000378:metabolism*; D013205:Staphylococcal Protein A / Q000378:metabolism; D014155:Transcobalamins / Q000378:metabolism; D014805:Vitamin B 12 / Q000378:metabolism*
chemical_list: C029152:G-substrate; D009419:Nerve Tissue Proteins; D011956:Receptors, Cell Surface; D013205:Staphylococcal Protein A; D014155:Transcobalamins; C497415:vitamin B12 receptor protein, human; D004492:Edetic Acid; D014805:Vitamin B 12