1NQH

OUTER MEMBRANE COBALAMIN TRANSPORTER (BTUB) FROM E. COLI, WITH BOUND CALCIUM AND CYANOCOBALAMIN (VITAMIN B12) SUBSTRATE


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.1 Å
  • R-Value Free: 0.265 
  • R-Value Work: 0.224 

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.Mol.Biol. 10: 394-401

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

  • 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.,Sect.D 59: 509


    Organizational Affiliation

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




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
VITAMIN B12 RECEPTOR
A
594Escherichia coli (strain K12)Gene Names: btuB (bfe, cer, dcrC)
Membrane protein
mpstruct
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))
Go to UniProtKB:  P06129
Small Molecules
Ligands 3 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
C8E
Query on C8E

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

Download SDF File 
Download CCD File 
A
CALCIUM ION
Ca
BHPQYMZQTOCNFJ-UHFFFAOYSA-N
 Ligand Interaction
CNC
Query on CNC

Download SDF File 
Download CCD File 
A
CO-CYANOCOBALAMIN
C63 H88 Co N14 O14 P
OEEKSCBDGPRZJZ-BYLSPCLQSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 3.1 Å
  • R-Value Free: 0.265 
  • R-Value Work: 0.224 
  • Space Group: P 31 2 1
Unit Cell:
Length (Å)Angle (°)
a = 81.687α = 90.00
b = 81.687β = 90.00
c = 225.814γ = 120.00
Software Package:
Software NamePurpose
HKL-2000data reduction
REFMACrefinement
AMoREphasing
HKL-2000data collection
SCALEPACKdata scaling
SHARPphasing

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

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