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transcobalamin-1; TC-1; transcobalamin I; cobalophilin R; R-binder; TC I; TCI (TCN1 TC1)
Function:
- binds to vit B12 in saliva protecting vit B12 in the acidic environment of the stomach
- in the duodenum, transcobalamin-1 releases vit B12 for binding to intrinsic factor
- transcobalamin-1 is the major reservoir of plasma cobalamin; it is typically 70-90% saturated
- plasma cobalamin bound to transcobalamin-1 is proababy metabolically inert since no cellular receptors for it have been identified
- transports cobalamin into cells [4]
- R-binder may be identical to transcobalamin-3 except for carbohydrate content
Structure:
- contains about 30% carbohydrates
- belongs to the eukaryotic cobalamin transport protein family
Compartment:
- found in plasma, amniotic fluid, milk, saliva, ascitic fluid, & granulocytes
Expression: neutrophil granule protein
Pharmacokinetics:
- elimination 1/2life of the transcobalamin-1/vit B12 complex in plasma is 1 hour
Laboratory:
- alias cobolaphilin R for rapidly migrating on electrophoresis
Specific
transcobalamin 3
General
transcobalamin
Properties
SIZE: entity length = 433 aa
MW = 48 kD
COMPARTMENT: plasma
MOTIF: signal sequence {1-23}
cysteine residue {C26}
MODIFICATION: cysteine residue {C265}
cysteine residue {C105}
MODIFICATION: cysteine residue {C308}
cysteine residue {C155}
MODIFICATION: cysteine residue {C197}
N-glycosylation site {N160}
cysteine residue {C197}
MODIFICATION: cysteine residue {C155}
N-glycosylation site {N216}
cysteine residue {C265}
MODIFICATION: cysteine residue {C26}
cysteine residue {C308}
MODIFICATION: cysteine residue {C105}
N-glycosylation site {N316}
N-glycosylation site {N337}
N-glycosylation site {N343}
N-glycosylation site {N349}
N-glycosylation site {N354}
N-glycosylation site {N369}
Database Correlations
OMIM 189905
UniProt P20061
Pfam PF01122
Entrez Gene 6947
Kegg hsa:6947
References
- Clinical Diagnosis & Management by Laboratory Methods,
J.B. Henry (ed), W.B. Saunders Co., Philadelphia,
PA. 1991, pg 632
- Harrison's Online, Chapter 107, McGraw Hill, 2002
- Carmel R
Clinical Chemistry. 48:407-409. 2002
PMID: 11861432
http://www.clinchem.org/cgi/content/full/48/3/407?ijkey=793472d270daf818b0942b60af4b1ef7f4b997cc&keytype2=tf_ipsecsha
- UniProt :accession P20061