Biological Assembly 1  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 1 assigned by authors.

Biological Assembly 2  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 2 assigned by authors.

Biological Assembly 3  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 3 assigned by authors.

Biological Assembly 4  

 3D View: Structure | 1D-3D View | Electron Density | Validation Report | Ligand Interaction

Global Symmetry: Asymmetric - C1 
Global Stoichiometry: Monomer - A1 

Biological assembly 4 assigned by authors.

Macromolecule Content

• Total Structure Weight: 190.72 kDa 
• Atom Count: 14148 
• Modelled Residue Count: 1656 
• Deposited Residue Count: 1656 
• Unique protein chains: 1

2BB6

Structure of Cobalamin-complexed Bovine Transcobalamin in Monoclinic Crystal Form

• PDB DOI: 10.2210/pdb2BB6/pdb

• Classification: TRANSPORT PROTEIN
• Organism(s): Bos taurus
• Expression System: Komagataella pastoris
• Mutation(s): No 


• Deposited: 2005-10-17 Released: 2006-04-04 
• Deposition Author(s): Wuerges, J., Garau, G., Geremia, S., Fedosov, S.N., Petersen, T.E., Randaccio, L.

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Experimental Data Snapshot

• Method: X-RAY DIFFRACTION
• Resolution: 2.00 Å
• R-Value Free: 0.280 
• R-Value Work: 0.241 
• R-Value Observed: 0.243 

Literature

Structural basis for mammalian vitamin B12 transport by transcobalamin.

Wuerges, J., Garau, G., Geremia, S., Fedosov, S.N., Petersen, T.E., Randaccio, L.

(2006) Proc Natl Acad Sci U S A 103: 4386-4391

• PubMed: 16537422 
• DOI: 10.1073/pnas.0509099103
• Primary Citation of Related Structures:  
  2BB5, 2BB6, 2BBC


• PubMed Abstract: 
  

Cobalamin (Cbl, vitamin B(12)) serves for two essential cofactors in mammals. The pathway for its intestinal absorption, plasma transport, and cellular uptake uses cell surface receptors and three Cbl-transporting proteins, haptocorrin, intrinsic factor, and transcobalamin (TC). We present the structure determination of a member of the mammalian Cbl-transporter family. The crystal structures of recombinant human and bovine holo-TCs reveal a two-domain architecture, with an N-terminal alpha(6)-alpha(6) barrel and a smaller C-terminal domain. One Cbl molecule in base-on conformation is buried inside the domain interface. Structural data combined with previous binding assays indicate a domain motion in the first step of Cbl binding. In a second step, the weakly coordinated ligand H(2)O at the upper axial side of added H(2)O-Cbl is displaced by a histidine residue of the alpha(6)-alpha(6) barrel. Analysis of amino acid conservation on TC's surface in orthologous proteins suggests the location of the TC-receptor-recognition site in an extended region on the alpha(6)-alpha(6) barrel. The TC structure allows for the mapping of sites of amino acid variation due to polymorphisms of the human TC gene. Structural information is used to predict the overall fold of haptocorrin and intrinsic factor and permits a rational approach to the design of new Cbl-based bioconjugates for diagnostic or therapeutic drug delivery.

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Organizational Affiliation: 

Centre of Excellence in Biocrystallography, Department of Chemical Sciences, University of Trieste, Via L. Giorgieri 1, I-34127 Trieste, Italy.

Macromolecules

Entity ID: 1
Molecule	Chains	Sequence Length	Organism	Details	Image
Transcobalamin II	A, B, C, D	414	Bos taurus	Mutation(s): 0  Gene Names: TCN2, TC2
UniProt
Find proteins for Q9XSC9 (Bos taurus) Explore Q9XSC9  Go to UniProtKB:  Q9XSC9

Small Molecules

Ligands 2 Unique
ID	Chains	Name / Formula / InChI Key	2D Diagram
B12	F [auth A], H [auth B], J [auth C], L [auth D]	COBALAMIN C62 H89 Co N13 O14 P LKVIQTCSMMVGFU-DWSMJLPVSA-N
CL	E [auth A], G [auth B], I [auth C], K [auth D]	CHLORIDE ION Cl VEXZGXHMUGYJMC-UHFFFAOYSA-M

Experimental Data & Validation

Experimental Data

• Method: X-RAY DIFFRACTION
• Resolution: 2.00 Å
• R-Value Free: 0.280 
• R-Value Work: 0.241 
• R-Value Observed: 0.243 
• Space Group: P 1 2₁ 1

Unit Cell:

Length ( Å )	Angle ( ˚ )
a = 95.826	α = 90
b = 100.664	β = 97.16
c = 99.143	γ = 90

Software Package:

Software Name	Purpose
DENZO	data reduction
SCALEPACK	data scaling
REFMAC	refinement
PDB_EXTRACT	data extraction
AMoRE	phasing

Structure Validation

Entry History 

Deposition Data

• Deposited Date: 2005-10-17 
• Released Date: 2006-04-04 
Deposition Author(s): Wuerges, J., Garau, G., Geremia, S., Fedosov, S.N., Petersen, T.E., Randaccio, L.

Revision History  

• Version 1.0: 2006-04-04
  Type: Initial release
  
• Version 1.1: 2008-05-01
  Changes: Version format compliance
• Version 1.2: 2011-07-13
  Changes: Version format compliance
• Version 1.3: 2012-10-24
  Changes: Non-polymer description
• Version 1.4: 2017-10-11
  Changes: Refinement description