3R6U

Crystal structure of choline binding protein OpuBC from Bacillus subtilis


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.61 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.160 

wwPDB Validation 3D Report Full Report


This is version 1.2 of the entry. See complete history

Literature

The Crystal Structure of the Substrate-Binding Protein OpuBC from Bacillus subtilis in Complex with Choline.

Pittelkow, M.Tschapek, B.Smits, S.H.Schmitt, L.Bremer, E.

(2011) J.Mol.Biol. 411: 53-67

  • DOI: 10.1016/j.jmb.2011.05.037

  • PubMed Abstract: 
  • Bacillus subtilis can synthesize the compatible solute glycine betaine as an osmoprotectant from an exogenous supply of the precursor choline. Import of choline is mediated by two osmotically inducible ABC transport systems: OpuB and OpuC. OpuC catal ...

    Bacillus subtilis can synthesize the compatible solute glycine betaine as an osmoprotectant from an exogenous supply of the precursor choline. Import of choline is mediated by two osmotically inducible ABC transport systems: OpuB and OpuC. OpuC catalyzes the import of various osmoprotectants, whereas OpuB is highly specific for choline. OpuBC is the substrate-binding protein of the OpuB transporter, and we have analyzed the affinity of the OpuBC/choline complex by intrinsic tryptophan fluorescence and determined a K(d) value of about 30 μM. The X-ray crystal structure of the OpuBC/choline complex was solved at a resolution of 1.6 Å and revealed a fold typical of class II substrate-binding proteins. The positively charged trimethylammonium head group of choline is wedged into an aromatic cage formed by four tyrosine residues and is bound via cation-pi interactions. The hydroxyl group of choline protrudes out of this aromatic cage and makes a single interaction with residue Gln19. The substitution of this residue by Ala decreases choline binding affinity by approximately 15-fold. A water network stabilizes choline within its substrate-binding site and promotes indirect interactions between the two lobes of the OpuBC protein. Disruption of this intricate water network by site-directed mutagenesis of selected residues in OpuBC either strongly reduces choline binding affinity (between 18-fold and 25-fold) or abrogates ligand binding. The crystal structure of the OpuBC/choline complex provides a rational for the observed choline specificity of the OpuB ABC importer in vivo and explains its inability to catalyze the import of glycine betaine into osmotically stressed B. subtilis cells.


    Organizational Affiliation

    Laboratory for Microbiology, Department of Biology, Philipps University Marburg, Marburg, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
Choline-binding protein
A
284Bacillus subtilis (strain 168)Mutation(s): 0 
Gene Names: opuBC (proX)
Find proteins for Q45462 (Bacillus subtilis (strain 168))
Go to UniProtKB:  Q45462
Small Molecules
Ligands 1 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
CHT
Query on CHT

Download SDF File 
Download CCD File 
A
CHOLINE ION
C5 H14 N O
OEYIOHPDSNJKLS-UHFFFAOYSA-N
 Ligand Interaction
External Ligand Annotations 
IDBinding Affinity (Sequence Identity %)
CHTIC50: 30500 nM BINDINGMOAD
CHTKd: 30500 nM PDBBIND
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.61 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.160 
  • Space Group: P 1 21 1
Unit Cell:
Length (Å)Angle (°)
a = 29.900α = 90.00
b = 66.900β = 93.60
c = 64.100γ = 90.00
Software Package:
Software NamePurpose
XSCALEdata scaling
PHASERphasing
DNAdata collection
XDSdata reduction
REFMACrefinement

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2011-06-15
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2011-08-10
    Type: Database references