Cobalamin (vitamin B12)-binding protein (IPR002157)

Short name: Cbl-bd_prot

Overlapping homologous superfamilies


Family relationships



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 alpha(6)-alpha(6) barrel, and a smaller C-terminal domain [PMID: 16537422]. 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 beta-hairpin motif found in the smaller C-terminal domain [PMID: 17274763].

GO terms

Biological Process

GO:0015889 cobalamin transport

Molecular Function

GO:0031419 cobalamin binding

Cellular Component

No terms assigned in this category.

Contributing signatures

Signatures from InterPro member databases are used to construct an entry.
PROSITE patterns