Mapping the functional domains of TCblR/CD320, the receptor for cellular uptake of transcobalamin‐bound cobalamin
| Autor: | Yasumi Nakayama, Jeffrey M. Sequeira, Edward V. Quadros, Wenxia Jiang |
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| Rok vydání: | 2013 |
| Předmět: |
media_common.quotation_subject
Amino Acid Motifs Green Fluorescent Proteins Molecular Sequence Data PDZ domain PDZ Domains Receptors Cell Surface macromolecular substances Plasma protein binding Biology Ligands Binding Competitive Biochemistry Cobalamin Research Communications chemistry.chemical_compound Transcobalamin Antigens CD Cell surface receptor hemic and lymphatic diseases Protein Interaction Mapping Genetics Humans Protein Interaction Domains and Motifs Amino Acid Sequence Binding site Internalization Molecular Biology Sequence Deletion media_common Transcobalamins Binding Sites Ligand (biochemistry) Endocytosis Kinetics Vitamin B 12 HEK293 Cells Microscopy Fluorescence Receptors LDL chemistry Mutation Protein Binding Biotechnology |
| Zdroj: | The FASEB Journal. 27:2988-2994 |
| ISSN: | 1530-6860 0892-6638 |
| Popis: | The membrane receptor TCblR/CD320 binds transcobalamin (TC) saturated with vitamin B12 [cobalamin (Cbl)] and mediates cellular uptake of the vitamin. The specificity of TC for Cbl and of the receptor for TC-Cbl ensures efficient uptake of Cbl into cells. The high-affinity interaction of TCblR with TC-Cbl (Ka=10 nM−1) was investigated using deletions and mutations of amino acid sequences in TCblR. Only the extracellular region (aa 32–229) is needed for TC-Cbl binding, but the N-glycosylation sites (N126, N195, and N213) are of no importance for this function. Deleting the cysteine-rich region (aa 95–141) that separates the two low-density lipoprotein receptor type A (LDLR-A) domains does not affect TC-Cbl binding (Ka = 19–24 nM−1). The two LDLR-A domains (aa 54–89 and 132–167) with the negatively charged acidic residues involved in Ca2+ binding are critical determinants of ligand binding. The cytoplasmic tail is apparently crucial for internalization of the ligand. Within this region, the RPLGLL motif and the PDZ binding motifs (QERL/KESL) appear to be involved in initiating and completing the process of ligand internalization. Mutations and deletions of these regions involved in binding and internalization of TC-Cbl are likely to produce the biochemical and clinical phenotype of Cbl deficiency.—Jiang, W., Nakayama, Y., Sequeira, J. M., Quadros, E. V. Mapping the functional domains of TCblR/CD320, the receptor for cellular uptake of transcobalamin-bound cobalamin. |
| Databáze: | OpenAIRE |
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