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intrinsic factor; gastric intrinsic factor; IF; INF (GIF, IFMH)
Function:
- binds to cobalamin (vit B12) & serves as a ligand for a specific receptor in the mucosal brush border of the ileum; promotes absorption cobalamin by receptor-mediated endocytosis
- cobalamin/intrinsic factor complex is resistant to proteolytic digestion
Structure:
- belongs to the eukaryotic cobalamin transport proteins family
Compartment: secreted
Expression:
- gastric mucosa
- produced by parietal cells of the stomach
- secretion of intrinsic factor parallels that of HCl
- secretion of vit B12 is inhibited by proton pump inhibitors (clinical significance unknown)
Pathology:
- deficiency of intrinsic factor gives rise to vitamin B12 deficiency (pernicious anemia)
- defects in the gene for intrinsic factor (GIF) are the cause of congenital pernicious anemia
Related
anti-intrinsic factor antibody (INTRINS)
cobalamin-binding protein
pernicious anemia; autoimmune gastritis
vitamin B12 deficiency
vitamin B12; cobalamin
General
mucoprotein
secreted protein
Properties
SIZE: entity length = 417 aa
MW = 45 kD
COMPARTMENT: extracellular compartment
MOTIF: signal sequence {1-18}
cysteine residue {C26}
MODIFICATION: cysteine residue {C246}
cysteine residue {C103}
MODIFICATION: cysteine residue {C288}
cysteine residue {C143}
MODIFICATION: cysteine residue {C182}
binding site
SITE: 171-171
FOR-BINDING-OF: Cobalamin
cysteine residue {C182}
MODIFICATION: cysteine residue {C143}
binding site
SITE: 222-222
FOR-BINDING-OF: Cobalamin
cysteine residue {C246}
MODIFICATION: cysteine residue {C26}
binding site
SITE: 270-270
FOR-BINDING-OF: cobalamin
cysteine residue {C288}
MODIFICATION: cysteine residue {C103}
N-glycosylation site {N311}
N-glycosylation site {N330}
N-glycosylation site {N334}
binding site
SITE: 365-370
FOR-BINDING-OF: cobalamin
binding site
SITE: 386-395
FOR-BINDING-OF: cobalamin
N-glycosylation site {N413}
Database Correlations
OMIM correlations
MORBIDMAP 609342
UniProt P27352
Pfam PF01122
Entrez Gene 2694
Kegg hsa:2694
References
- Harrison's Online, Chapter 107, McGraw Hill, 2002
- GeneReviews
https://www.genecards.org/cgi-bin/carddisp.pl?gene=GIF
- Wikipedia - intrinsic factor entry
http://en.wikipedia.org/wiki/intrinsic_factor
- UniProt :accession P27352