F
IPR002157

Cobalamin (vitamin B12)-binding protein

InterPro entry
Short nameCbl-bd_prot

Description

Cobalamin (Cbl or vitamin B12) is only accessible through diet in mammals. Absorption, plasma transport and cellular uptake of Cbl in mammals involves three Cbl-transporting proteins, which are listed below in order of increasing Cbl-specificity:


 * Haptocorrin (cobalophilin), which binds Cbl and Cbl-derivatives such as cobinamide; it may play a role in preventing the absorption of cobalamin analogues produced by bacteria.
 * Transcobalamin (TC), which transport Cbl from blood to cells.
 * Intrinsic factor (IF), which promotes Cbl absorption in the ileum by specific receptor-mediated endocytosis.


The structure of TC reveals a two-domain structure, an N-terminal α(6)-α(6) barrel, and a smaller C-terminal domain
[1]
. Many interactions between Cbl and its binding site in the interface of the two domains are conserved among the other Cbl transporters. Specificity for Cbl between the different transporters may reside in a β-hairpin motif found in the smaller C-terminal domain
[2]
.

References

1.Structural basis for mammalian vitamin B12 transport by transcobalamin. Wuerges J, Garau G, Geremia S, Fedosov SN, Petersen TE, Randaccio L. Proc. Natl. Acad. Sci. U.S.A. 103, 4386-91, (2006). View articlePMID: 16537422

2.Structural study on ligand specificity of human vitamin B12 transporters. Wuerges J, Geremia S, Randaccio L. Biochem. J. 403, 431-40, (2007). View articlePMID: 17274763

GO terms

cellular component

  • None

Cross References

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