1NQE

OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.196 

wwPDB Validation   3D Report Full Report


This is version 1.2 of the entry. See complete history


Literature

Substrate-induced transmembrane signaling in the cobalamin transporter BtuB

Chimento, D.P.Mohanty, A.K.Kadner, R.J.Wiener, M.C.

(2003) Nat Struct Biol 10: 394-401

  • DOI: 10.1038/nsb914
  • Primary Citation of Related Structures:  
    1NQH, 1NQG, 1NQF, 1NQE

  • PubMed Abstract: 
  • The outer membranes of Gram-negative bacteria possess transport proteins essential for uptake of scarce nutrients. In TonB-dependent transporters, a conserved sequence of seven residues, the Ton box, faces the periplasm and interacts with the inner m ...

    The outer membranes of Gram-negative bacteria possess transport proteins essential for uptake of scarce nutrients. In TonB-dependent transporters, a conserved sequence of seven residues, the Ton box, faces the periplasm and interacts with the inner membrane TonB protein to energize an active transport cycle. A critical mechanistic step is the structural change in the Ton box of the transporter upon substrate binding; this essential transmembrane signaling event increases the affinity of the transporter for TonB and enables active transport to proceed. We have solved crystal structures of BtuB, the outer membrane cobalamin transporter from Escherichia coli, in the absence and presence of cyanocobalamin (vitamin B(12)). In these structures, the Ton box is ordered and undergoes a conformational change in the presence of bound substrate. Calcium has been implicated as a necessary factor for the high-affinity binding (K(d) approximately 0.3 nM) of cyanocobalamin to BtuB. We observe two bound calcium ions that order three extracellular loops of BtuB, thus providing a direct (and unusual) structural role for calcium.


    Related Citations: 
    • Crystallization and initial X-ray diffraction of BtuB, the integral membrane cobalamin transporter of Escherichia coli
      Chimento, D.P., Mohanty, A.K., Kadner, R.J., Wiener, M.C.
      (2003) Acta Crystallogr D Biol Crystallogr 59: 509

    Organizational Affiliation

    Department of Microbiology, University of Virginia, Charlottesville, Virginia 22908, USA.



Macromolecules
Find similar proteins by:  (by identity cutoff)  |  Structure
Entity ID: 1
MoleculeChainsSequence LengthOrganismDetailsImage
Vitamin B12 receptorA594Escherichia coliMutation(s): 0 
Gene Names: btuB
Membrane protein
Mpstruc
Group: 
TRANSMEMBRANE PROTEINS: BETA-BARREL
Sub Group: 
Beta-Barrel Membrane Proteins: Monomeric/Dimeric
Protein: 
apo BtuB cobalamin transporter
Find proteins for P06129 (Escherichia coli (strain K12))
Explore P06129 
Go to UniProtKB:  P06129
Protein Feature View
Expand
  • Reference Sequence
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
C8E
Query on C8E

Download CCD File 
A
(HYDROXYETHYLOXY)TRI(ETHYLOXY)OCTANE
C16 H34 O5
FEOZZFHAVXYAMB-UHFFFAOYSA-N
 Ligand Interaction
MG
Query on MG

Download CCD File 
A
MAGNESIUM ION
Mg
JLVVSXFLKOJNIY-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 2.00 Å
  • R-Value Free: 0.232 
  • R-Value Work: 0.194 
  • R-Value Observed: 0.196 
  • Space Group: P 31 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 81.59α = 90
b = 81.59β = 90
c = 210.078γ = 120
Software Package:
Software NamePurpose
REFMACrefinement
DENZOdata reduction
SCALEPACKdata scaling
AMoREphasing

Structure Validation

View Full Validation Report



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2003-04-29
    Type: Initial release
  • Version 1.1: 2007-10-16
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Advisory, Version format compliance