Crystal structure of EXPB1 (Zea m 1), a beta-expansin and group-1 pollen allergen from maize

Experimental Data Snapshot

  • Resolution: 2.75 Å
  • R-Value Free: 0.290 
  • R-Value Work: 0.233 
  • R-Value Observed: 0.233 

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Crystal structure and activities of EXPB1 (Zea m 1), a beta-expansin and group-1 pollen allergen from maize.

Yennawar, N.H.Li, L.C.Dudzinski, D.M.Tabuchi, A.Cosgrove, D.J.

(2006) Proc Natl Acad Sci U S A 103: 14664-14671

  • DOI: https://doi.org/10.1073/pnas.0605979103
  • Primary Citation of Related Structures:  

  • PubMed Abstract: 

    Expansins are small extracellular proteins that promote turgor-driven extension of plant cell walls. EXPB1 (also called Zea m 1) is a member of the beta-expansin subfamily known in the allergen literature as group-1 grass pollen allergens. EXPB1 induces extension and stress relaxation of grass cell walls. To help elucidate expansin's mechanism of wall loosening, we determined the structure of EXPB1 by x-ray crystallography to 2.75-A resolution. EXPB1 consists of two domains closely packed and aligned so as to form a long, shallow groove with potential to bind a glycan backbone of approximately 10 sugar residues. The structure of EXPB1 domain 1 resembles that of family-45 glycoside hydrolase (GH45), with conservation of most of the residues in the catalytic site. However, EXPB1 lacks a second aspartate that serves as the catalytic base required for hydrolytic activity in GH45 enzymes. Domain 2 of EXPB1 is an Ig-like beta-sandwich, with aromatic and polar residues that form a potential surface for polysaccharide binding in line with the glycan binding cleft of domain 1. EXPB1 binds to maize cell walls, most strongly to xylans, causing swelling of the cell wall. Tests for hydrolytic activity by EXPB1 with various wall polysaccharides proved negative. Moreover, GH45 enzymes and a GH45-related protein called "swollenin" lacked wall extension activity comparable to that of expansins. We propose a model of expansin action in which EXPB1 facilitates the local movement and stress relaxation of arabinoxylan-cellulose networks within the wall by noncovalent rearrangement of its target.

  • Organizational Affiliation

    Huck Institutes of the Life Sciences and Department of Biology, Pennsylvania State University, University Park, PA 16802, USA.

Find similar proteins by:  (by identity cutoff)  |  3D Structure
Entity ID: 1
MoleculeChains Sequence LengthOrganismDetailsImage
Beta-expansin 1aA [auth X]245Zea maysMutation(s): 1 
Find proteins for P58738 (Zea mays)
Explore P58738 
Go to UniProtKB:  P58738
Entity Groups  
Sequence Clusters30% Identity50% Identity70% Identity90% Identity95% Identity100% Identity
UniProt GroupP58738
Sequence Annotations
  • Reference Sequence


Entity ID: 2
MoleculeChains Length2D Diagram Glycosylation3D Interactions
alpha-D-xylopyranose-(1-2)-[alpha-D-mannopyranose-(1-3)][alpha-D-mannopyranose-(1-6)]alpha-D-mannopyranose-(1-4)-2-acetamido-2-deoxy-beta-D-glucopyranose-(1-4)-[alpha-D-fucopyranose-(1-3)]2-acetamido-2-deoxy-beta-D-glucopyranoseB [auth A]7N-Glycosylation
Glycosylation Resources
GlyTouCan:  G47905TF
GlyCosmos:  G47905TF
Small Molecules
Modified Residues  1 Unique
IDChains TypeFormula2D DiagramParent
Query on HYP
Experimental Data & Validation

Experimental Data

  • Resolution: 2.75 Å
  • R-Value Free: 0.290 
  • R-Value Work: 0.233 
  • R-Value Observed: 0.233 
  • Space Group: C 1 2 1
Unit Cell:
Length ( Å )Angle ( ˚ )
a = 113.408α = 90
b = 44.512β = 124.64
c = 69.467γ = 90
Software Package:
Software NamePurpose
DENZOdata reduction
SCALEPACKdata scaling
PDB_EXTRACTdata extraction
CrystalCleardata reduction

Structure Validation

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Entry History 

Deposition Data

Revision History  (Full details and data files)

  • Version 1.0: 2006-08-22
    Type: Initial release
  • Version 1.1: 2008-05-01
    Changes: Version format compliance
  • Version 1.2: 2011-07-13
    Changes: Non-polymer description, Version format compliance
  • Version 1.3: 2017-10-18
    Changes: Refinement description
  • Version 2.0: 2020-07-29
    Type: Remediation
    Reason: Carbohydrate remediation
    Changes: Advisory, Atomic model, Data collection, Database references, Derived calculations, Structure summary
  • Version 2.1: 2023-08-30
    Changes: Data collection, Database references, Refinement description, Structure summary