Søren Kragh Moestrup

Molecular dissection of the intrinsic factor-vitamin B12 receptor, cubilin, discloses regions important for membrane association and ligand binding.

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Cubilin, the receptor for intrinsic factor-vitamin B12, is a novel type of high molecular weight receptor consisting of a 27 CUB (complement components C1r/C1s, Uegf, and bone morphogenic protein-1) domain cluster preceded by 8 epidermal growth factor repeats and a short N-terminal sequence. In addition to binding the vitamin B12-carrier complex, cubilin also binds receptor-associated protein. To delineate the structures for membrane association and ligand binding we established a panel of stable transfected Chinese hamster ovary cells expressing overlapping segments of rat cubilin. Analysis of conditioned media and cell extracts of transfected cells revealed that the N-terminal cubilin region conveys membrane association. Helical plotting of this region demonstrated a conserved amphipathic helix pattern (Lys74-Glu109) as a candidate site for hydrophobic interactions. Ligand affinity chromatography and surface plasmon resonance analysis of the secreted cubilin fragments showed ligand binding in the CUB domain region. Further dissection of binding-active fragments localized the binding site for intrinsic factor-vitamin B12 to CUB domains 5-8 and a receptor-associated protein-binding site to CUB domains 13-14. In conclusion, the N-terminal cubilin region seems crucial for membrane association, whereas the CUB domain cluster harbors distinct sites for ligand binding.
Udgivelsesdato: 1999-Jul-16
Original languageEnglish
JournalJournal of Biological Chemistry
Pages (from-to)20540-4
Number of pages4
Publication statusPublished - 1999

    Research areas

  • Amino Acid Sequence, Animals, Binding Sites, CHO Cells, Cell Membrane, Cricetinae, Humans, Intrinsic Factor, Ligands, Membrane Glycoproteins, Molecular Sequence Data, Receptors, Cell Surface, Recombinant Proteins, Surface Plasmon Resonance, Swine, Vitamin B 12

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