Structure of Escherichia coli PgaB C-terminal domain in complex with N-acetylglucosamine

Experimental Data Snapshot

  • Resolution: 1.65 Å
  • R-Value Free: 0.195 
  • R-Value Work: 0.157 
  • R-Value Observed: 0.159 

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This is version 1.6 of the entry. See complete history


Modification and periplasmic translocation of the biofilm exopolysaccharide poly-beta-1,6-N-acetyl-D-glucosamine.

Little, D.J.Li, G.Ing, C.DiFrancesco, B.R.Bamford, N.C.Robinson, H.Nitz, M.Pomes, R.Howell, P.L.

(2014) Proc Natl Acad Sci U S A 111: 11013-11018

  • DOI: https://doi.org/10.1073/pnas.1406388111
  • Primary Citation of Related Structures:  
    4P7L, 4P7N, 4P7O, 4P7Q, 4P7R

  • PubMed Abstract: 

    Poly-β-1,6-N-acetyl-D-glucosamine (PNAG) is an exopolysaccharide produced by a wide variety of medically important bacteria. Polyglucosamine subunit B (PgaB) is responsible for the de-N-acetylation of PNAG, a process required for polymer export and biofilm formation. PgaB is located in the periplasm and likely bridges the inner membrane synthesis and outer membrane export machinery. Here, we present structural, functional, and molecular simulation data that suggest PgaB associates with PNAG continuously during periplasmic transport. We show that the association of PgaB's N- and C-terminal domains forms a cleft required for the binding and de-N-acetylation of PNAG. Molecular dynamics (MD) simulations of PgaB show a binding preference for N-acetylglucosamine (GlcNAc) to the N-terminal domain and glucosammonium to the C-terminal domain. Continuous ligand binding density is observed that extends around PgaB from the N-terminal domain active site to an electronegative groove on the C-terminal domain that would allow for a processive mechanism. PgaB's C-terminal domain (PgaB310-672) directly binds PNAG oligomers with dissociation constants of ∼1-3 mM, and the structures of PgaB310-672 in complex with β-1,6-(GlcNAc)6, GlcNAc, and glucosamine reveal a unique binding mode suitable for interaction with de-N-acetylated PNAG (dPNAG). Furthermore, PgaB310-672 contains a β-hairpin loop (βHL) important for binding PNAG that was disordered in previous PgaB42-655 structures and is highly dynamic in the MD simulations. We propose that conformational changes in PgaB310-672 mediated by the βHL on binding of PNAG/dPNAG play an important role in the targeting of the polymer for export and its release.

  • Organizational Affiliation

    Program in Molecular Structure and Function, Research Institute, The Hospital for Sick Children, Toronto, ON, Canada M5G 1X8;Department of Biochemistry, University of Toronto, Toronto, ON, Canada M5S 1A8;

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Poly-beta-1,6-N-acetyl-D-glucosamine N-deacetylase367Escherichia coli K-12Mutation(s): 0 
Gene Names: pgaBycdRb1023JW5142
EC: 3.5.1
Find proteins for P75906 (Escherichia coli (strain K12))
Explore P75906 
Go to UniProtKB:  P75906
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP75906
Sequence Annotations
  • Reference Sequence
Experimental Data & Validation

Experimental Data

  • Resolution: 1.65 Å
  • R-Value Free: 0.195 
  • R-Value Work: 0.157 
  • R-Value Observed: 0.159 
  • Space Group: P 21 21 21
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 42.38α = 90
b = 77.958β = 90
c = 115.276γ = 90
Software Package:
Software NamePurpose
HKL-2000data collection
HKL-2000data reduction
HKL-2000data scaling
Cootmodel building
PDB_EXTRACTdata extraction

Structure Validation

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Ligand Structure Quality Assessment 

Entry History & Funding Information

Deposition Data

Funding OrganizationLocationGrant Number
Canadian Institutes of Health Research (CIHR)Canada--

Revision History  (Full details and data files)

  • Version 1.0: 2014-07-02
    Type: Initial release
  • Version 1.1: 2014-07-23
    Changes: Database references
  • Version 1.2: 2014-10-01
    Changes: Database references
  • Version 1.3: 2017-11-22
    Changes: Database references, Derived calculations, Other, Refinement description, Source and taxonomy, Structure summary
  • Version 1.4: 2020-01-08
    Changes: Author supporting evidence
  • Version 1.5: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Data collection, Derived calculations, Refinement description, Structure summary
  • Version 1.6: 2023-09-27
    Changes: Data collection, Database references, Refinement description, Structure summary