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Blood. 2009 Jan 1;113(1):186-92. doi: 10.1182/blood-2008-05-158949. Epub 2008 Sep 8.

The protein and the gene encoding the receptor for the cellular uptake of transcobalamin-bound cobalamin.

Author information

1
Departments of Medicine and Cell Biology, State University of New York Downstate Medical Center, 450 Clarkson Avenue, Brooklyn, NY 11203, USA. Edward.Quadros@downstate.edu

Abstract

The transcobalamin (TC, TCII) receptor (TCblR) on the plasma membrane binds TC- cobalamin (Cbl) and internalizes the complex by endocytosis. This receptor was purified from human placental membranes by affinity chromatography. Tryptic digest of the protein extracted from a sodium dodecyl sulfate-polyacrylamide gel electrophoresis gel and subjected to liquid chromatography/mass spectrometry identified 4 peptides that matched with a membrane protein in the data bank. TCblR belongs to the low-density lipoprotein receptor family, with 2 low-density lipoprotein receptor type A domains separated by a complement-like cysteine-rich region. The 282-amino acid sequence includes a signal peptide of 31 residues, extracellular domain of 198 residues, a transmembrane region of 21 residues, and a cytoplasmic domain of 32 residues. The binding of TC-Cbl does not require the cytoplasmic domain or its orientation in the plasma membrane because the recombinant extracellular domain binds TC-Cbl with high affinity and specificity. The protein is heavily glycosylated and accounts for the 58-kDa size by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The human gene first identified as 8D6A and more recently as CD 320 encoding TCblR is located at p13.2 on the short arm of chromosome 19, spans a length of 6.224 kb, and is composed of 5 exons and 4 introns.

PMID:
18779389
PMCID:
PMC2614632
DOI:
10.1182/blood-2008-05-158949
[Indexed for MEDLINE]
Free PMC Article

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