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Crystal structures and biochemical characterization of the bacterial solute receptor AcbH reveal an unprecedented exclusive substrate preference for b-D-galactopyranose


Experimental Data Snapshot

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.6 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.167 

wwPDB Validation 3D Report Full Report


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Literature

Crystal structures of the bacterial solute receptor AcbH displaying an exclusive substrate preference for beta-D-galactopyranose

Licht, A.Bulut, H.Scheffel, F.Daumke, O.Wehmeier, U.F.Saenger, W.Schneider, E.Vahedi-Faridi, A.

(2011) J.Mol.Biol. 406: 92-105

  • DOI: 10.1016/j.jmb.2010.11.048
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 
  • Solute receptors (binding proteins) are indispensable components of canonical ATP-binding cassette importers in prokaryotes. Here, we report on the characterization and crystal structures in the closed and open conformations of AcbH, the solute recep ...

    Solute receptors (binding proteins) are indispensable components of canonical ATP-binding cassette importers in prokaryotes. Here, we report on the characterization and crystal structures in the closed and open conformations of AcbH, the solute receptor of the putative carbohydrate transporter AcbFG which is encoded in the acarbose (acarviosyl-1,4-maltose) biosynthetic gene cluster from Actinoplanes sp. SE50/110. Binding assays identified AcbH as a high-affinity monosaccharide-binding protein with a dissociation constant (K(d)) for β-d-galactopyranose of 9.8±1.0 nM. Neither galactose-containing di- and trisaccharides, such as lactose and raffinose, nor monosaccharides including d-galacturonic acid, l-arabinose, d-xylose and l-rhamnose competed with [(1)(4)C]galactose for binding to AcbH. Moreover, AcbH does not bind d-glucose, which is a common property of all but one d-galactose-binding proteins characterized to date. Strikingly, determination of the X-ray structure revealed that AcbH is structurally homologous to maltose-binding proteins rather than to glucose-binding proteins. Two helices are inserted in the substrate-binding pocket, which reduces the cavity size and allows the exclusive binding of monosaccharides, specifically β-d-galactopyranose, in the (4)C(1) conformation. Site-directed mutagenesis of three residues from the binding pocket (Arg82, Asp361 and Arg362) that interact with the axially oriented O4-H hydroxyl of the bound galactopyranose and subsequent functional analysis indicated that these residues are crucial for galactose binding. To our knowledge, this is the first report of the tertiary structure of a solute receptor with exclusive affinity for β-d-galactopyranose. The putative role of a galactose import system in the context of acarbose metabolism in Actinoplanes sp. is discussed.


    Organizational Affiliation

    Institut für Biologie, AG Bakterienphysiologie, Humboldt Universität zu Berlin, Chausseestr. 117, D-10115 Berlin, Germany.




Macromolecules

Find similar proteins by: Sequence  |  Structure

Entity ID: 1
MoleculeChainsSequence LengthOrganismDetails
ABC transporter binding protein AcbH
A
415Actinoplanes sp. (strain ATCC 31044 / CBS 674.73 / SE50/110)Mutation(s): 2 
Gene Names: AcbH (acbH)
Find proteins for Q27GR2 (Actinoplanes sp. (strain ATCC 31044 / CBS 674.73 / SE50/110))
Go to UniProtKB:  Q27GR2
Small Molecules
Ligands 2 Unique
IDChainsName / Formula / InChI Key2D Diagram3D Interactions
SO4
Query on SO4

Download SDF File 
Download CCD File 
A
SULFATE ION
O4 S
QAOWNCQODCNURD-UHFFFAOYSA-L
 Ligand Interaction
GOL
Query on GOL

Download SDF File 
Download CCD File 
A
GLYCEROL
GLYCERIN; PROPANE-1,2,3-TRIOL
C3 H8 O3
PEDCQBHIVMGVHV-UHFFFAOYSA-N
 Ligand Interaction
Experimental Data & Validation

Experimental Data

  • Method: X-RAY DIFFRACTION
  • Resolution: 1.6 Å
  • R-Value Free: 0.210 
  • R-Value Work: 0.167 
  • Space Group: P 21 21 21
Unit Cell:
Length (Å)Angle (°)
a = 39.507α = 90.00
b = 88.910β = 90.00
c = 102.678γ = 90.00
Software Package:
Software NamePurpose
PDB_EXTRACTdata extraction
ADSCdata collection
PHASERphasing
REFMACrefinement
XSCALEdata scaling

Structure Validation

View Full Validation Report or Ramachandran Plots



Entry History 

Deposition Data

Revision History 

  • Version 1.0: 2010-12-29
    Type: Initial release
  • Version 1.1: 2011-07-13
    Type: Version format compliance
  • Version 1.2: 2014-03-26
    Type: Database references